Commit Graph

1546 Commits

Author SHA1 Message Date
Mel Gorman
1a687c2e9a mm: sched: numa: Control enabling and disabling of NUMA balancing
This patch adds Kconfig options and kernel parameters to allow the
enabling and disabling of automatic NUMA balancing. The existance
of such a switch was and is very important when debugging problems
related to transparent hugepages and we should have the same for
automatic NUMA placement.

Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11 14:42:55 +00:00
Mel Gorman
b8593bfda1 mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrate
The PTE scanning rate and fault rates are two of the biggest sources of
system CPU overhead with automatic NUMA placement.  Ideally a proper policy
would detect if a workload was properly placed, schedule and adjust the
PTE scanning rate accordingly. We do not track the necessary information
to do that but we at least know if we migrated or not.

This patch scans slower if a page was not migrated as the result of a
NUMA hinting fault up to sysctl_numa_balancing_scan_period_max which is
now higher than the previous default. Once every minute it will reset
the scanner in case of phase changes.

This is hilariously crude and the numbers are arbitrary. Workloads will
converge quite slowly in comparison to what a proper policy should be able
to do. On the plus side, we will chew up less CPU for workloads that have
no need for automatic balancing.

Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11 14:42:55 +00:00
Mel Gorman
fb003b80da sched: numa: Slowly increase the scanning period as NUMA faults are handled
Currently the rate of scanning for an address space is controlled
by the individual tasks. The next scan is simply determined by
2*p->numa_scan_period.

The 2*p->numa_scan_period is arbitrary and never changes. At this point
there is still no proper policy that decides if a task or process is
properly placed. It just scans and assumes the next NUMA fault will
place it properly. As it is assumed that pages will get properly placed
over time, increase the scan window each time a fault is incurred. This
is a big assumption as noted in the comments.

It should be noted that changing to p->numa_scan_period will increase
system CPU usage because now the scanning rate has effectively doubled.
If that is a problem then the min_rate should be made 200ms instead of
restoring the 2* logic.

Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11 14:42:51 +00:00
Mel Gorman
e14808b49f mm: numa: Rate limit setting of pte_numa if node is saturated
If there are a large number of NUMA hinting faults and all of them
are resulting in migrations it may indicate that memory is just
bouncing uselessly around. NUMA balancing cost is likely exceeding
any benefit from locality. Rate limit the PTE updates if the node
is migration rate-limited. As noted in the comments, this distorts
the NUMA faulting statistics.

Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11 14:42:51 +00:00
Peter Zijlstra
4b96a29ba8 mm: sched: numa: Implement slow start for working set sampling
Add a 1 second delay before starting to scan the working set of
a task and starting to balance it amongst nodes.

[ note that before the constant per task WSS sampling rate patch
  the initial scan would happen much later still, in effect that
  patch caused this regression. ]

The theory is that short-run tasks benefit very little from NUMA
placement: they come and go, and they better stick to the node
they were started on. As tasks mature and rebalance to other CPUs
and nodes, so does their NUMA placement have to change and so
does it start to matter more and more.

In practice this change fixes an observable kbuild regression:

   # [ a perf stat --null --repeat 10 test of ten bzImage builds to /dev/shm ]

   !NUMA:
   45.291088843 seconds time elapsed                                          ( +-  0.40% )
   45.154231752 seconds time elapsed                                          ( +-  0.36% )

   +NUMA, no slow start:
   46.172308123 seconds time elapsed                                          ( +-  0.30% )
   46.343168745 seconds time elapsed                                          ( +-  0.25% )

   +NUMA, 1 sec slow start:
   45.224189155 seconds time elapsed                                          ( +-  0.25% )
   45.160866532 seconds time elapsed                                          ( +-  0.17% )

and it also fixes an observable perf bench (hackbench) regression:

   # perf stat --null --repeat 10 perf bench sched messaging

   -NUMA:

   -NUMA:                  0.246225691 seconds time elapsed                   ( +-  1.31% )
   +NUMA no slow start:    0.252620063 seconds time elapsed                   ( +-  1.13% )

   +NUMA 1sec delay:       0.248076230 seconds time elapsed                   ( +-  1.35% )

The implementation is simple and straightforward, most of the patch
deals with adding the /proc/sys/kernel/numa_balancing_scan_delay_ms tunable
knob.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
[ Wrote the changelog, ran measurements, tuned the default. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
2012-12-11 14:42:47 +00:00
Mel Gorman
9f40604cda sched, numa, mm: Count WS scanning against present PTEs, not virtual memory ranges
By accounting against the present PTEs, scanning speed reflects the
actual present (mapped) memory.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11 14:42:46 +00:00
Peter Zijlstra
6e5fb223e8 mm: sched: numa: Implement constant, per task Working Set Sampling (WSS) rate
Previously, to probe the working set of a task, we'd use
a very simple and crude method: mark all of its address
space PROT_NONE.

That method has various (obvious) disadvantages:

 - it samples the working set at dissimilar rates,
   giving some tasks a sampling quality advantage
   over others.

 - creates performance problems for tasks with very
   large working sets

 - over-samples processes with large address spaces but
   which only very rarely execute

Improve that method by keeping a rotating offset into the
address space that marks the current position of the scan,
and advance it by a constant rate (in a CPU cycles execution
proportional manner). If the offset reaches the last mapped
address of the mm then it then it starts over at the first
address.

The per-task nature of the working set sampling functionality in this tree
allows such constant rate, per task, execution-weight proportional sampling
of the working set, with an adaptive sampling interval/frequency that
goes from once per 100ms up to just once per 8 seconds.  The current
sampling volume is 256 MB per interval.

As tasks mature and converge their working set, so does the
sampling rate slow down to just a trickle, 256 MB per 8
seconds of CPU time executed.

This, beyond being adaptive, also rate-limits rarely
executing systems and does not over-sample on overloaded
systems.

[ In AutoNUMA speak, this patch deals with the effective sampling
  rate of the 'hinting page fault'. AutoNUMA's scanning is
  currently rate-limited, but it is also fundamentally
  single-threaded, executing in the knuma_scand kernel thread,
  so the limit in AutoNUMA is global and does not scale up with
  the number of CPUs, nor does it scan tasks in an execution
  proportional manner.

  So the idea of rate-limiting the scanning was first implemented
  in the AutoNUMA tree via a global rate limit. This patch goes
  beyond that by implementing an execution rate proportional
  working set sampling rate that is not implemented via a single
  global scanning daemon. ]

[ Dan Carpenter pointed out a possible NULL pointer dereference in the
  first version of this patch. ]

Based-on-idea-by: Andrea Arcangeli <aarcange@redhat.com>
Bug-Found-By: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
[ Wrote changelog and fixed bug. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
2012-12-11 14:42:46 +00:00
Peter Zijlstra
cbee9f88ec mm: numa: Add fault driven placement and migration
NOTE: This patch is based on "sched, numa, mm: Add fault driven
	placement and migration policy" but as it throws away all the policy
	to just leave a basic foundation I had to drop the signed-offs-by.

This patch creates a bare-bones method for setting PTEs pte_numa in the
context of the scheduler that when faulted later will be faulted onto the
node the CPU is running on.  In itself this does nothing useful but any
placement policy will fundamentally depend on receiving hints on placement
from fault context and doing something intelligent about it.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
2012-12-11 14:42:45 +00:00
Ingo Molnar
c1ad41f1f7 Revert "sched/autogroup: Fix crash on reboot when autogroup is disabled"
This reverts commit 5258f386ea,
because the underlying autogroups bug got fixed upstream in
a better way, via:

  fd8ef11730 Revert "sched, autogroup: Stop going ahead if autogroup is disabled"

Cc: Mike Galbraith <efault@gmx.de>
Cc: Yong Zhang <yong.zhang0@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-12-11 10:23:45 +01:00
Ingo Molnar
38130ec087 Some more cputime cleanups:
* Get rid of underscores polluting the vtime namespace
 
 * Consolidate context switch and tick handling
 
 * Improve debuggability by detecting irq unsafe callers
 
 Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
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Merge tag 'sched-cputime-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into sched/core

Pull more cputime cleanups from Frederic Weisbecker:

 * Get rid of underscores polluting the vtime namespace

 * Consolidate context switch and tick handling

 * Improve debuggability by detecting irq unsafe callers

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-12-08 15:44:43 +01:00
Mike Galbraith
fd8ef11730 Revert "sched, autogroup: Stop going ahead if autogroup is disabled"
This reverts commit 800d4d30c8.

Between commits 8323f26ce3 ("sched: Fix race in task_group()") and
800d4d30c8 ("sched, autogroup: Stop going ahead if autogroup is
disabled"), autogroup is a wreck.

With both applied, all you have to do to crash a box is disable
autogroup during boot up, then reboot..  boom, NULL pointer dereference
due to commit 800d4d30c8 not allowing autogroup to move things, and
commit 8323f26ce3 making that the only way to switch runqueues:

  BUG: unable to handle kernel NULL pointer dereference at           (null)
  IP: [<ffffffff81063ac0>] effective_load.isra.43+0x50/0x90
  Pid: 7047, comm: systemd-user-se Not tainted 3.6.8-smp #7 MEDIONPC MS-7502/MS-7502
  RIP: effective_load.isra.43+0x50/0x90
  Process systemd-user-se (pid: 7047, threadinfo ffff880221dde000, task ffff88022618b3a0)
  Call Trace:
    select_task_rq_fair+0x255/0x780
    try_to_wake_up+0x156/0x2c0
    wake_up_state+0xb/0x10
    signal_wake_up+0x28/0x40
    complete_signal+0x1d6/0x250
    __send_signal+0x170/0x310
    send_signal+0x40/0x80
    do_send_sig_info+0x47/0x90
    group_send_sig_info+0x4a/0x70
    kill_pid_info+0x3a/0x60
    sys_kill+0x97/0x1a0
    ? vfs_read+0x120/0x160
    ? sys_read+0x45/0x90
    system_call_fastpath+0x16/0x1b
  Code: 49 0f af 41 50 31 d2 49 f7 f0 48 83 f8 01 48 0f 46 c6 48 2b 07 48 8b bf 40 01 00 00 48 85 ff 74 3a 45 31 c0 48 8b 8f 50 01 00 00 <48> 8b 11 4c 8b 89 80 00 00 00 49 89 d2 48 01 d0 45 8b 59 58 4c
  RIP  [<ffffffff81063ac0>] effective_load.isra.43+0x50/0x90
   RSP <ffff880221ddfbd8>
  CR2: 0000000000000000

Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Yong Zhang <yong.zhang0@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@vger.kernel.org # 2.6.39+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-03 11:10:24 -08:00
Frederic Weisbecker
91d1aa43d3 context_tracking: New context tracking susbsystem
Create a new subsystem that probes on kernel boundaries
to keep track of the transitions between level contexts
with two basic initial contexts: user or kernel.

This is an abstraction of some RCU code that use such tracking
to implement its userspace extended quiescent state.

We need to pull this up from RCU into this new level of indirection
because this tracking is also going to be used to implement an "on
demand" generic virtual cputime accounting. A necessary step to
shutdown the tick while still accounting the cputime.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
[ paulmck: fix whitespace error and email address. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-11-30 11:40:07 -08:00
Frederic Weisbecker
fa09205783 cputime: Comment cputime's adjusting code
The reason for the scaling and monotonicity correction performed
by cputime_adjust() may not be immediately clear to the reviewer.

Add some comments to explain what happens there.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-11-28 17:08:20 +01:00
Frederic Weisbecker
d37f761dbd cputime: Consolidate cputime adjustment code
task_cputime_adjusted() and thread_group_cputime_adjusted()
essentially share the same code. They just don't use the same
source:

* The first function uses the cputime in the task struct and the
previous adjusted snapshot that ensures monotonicity.

* The second adds the cputime of all tasks in the group and the
previous adjusted snapshot of the whole group from the signal
structure.

Just consolidate the common code that does the adjustment. These
functions just need to fetch the values from the appropriate
source.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-11-28 17:08:10 +01:00
Frederic Weisbecker
e80d0a1ae8 cputime: Rename thread_group_times to thread_group_cputime_adjusted
We have thread_group_cputime() and thread_group_times(). The naming
doesn't provide enough information about the difference between
these two APIs.

To lower the confusion, rename thread_group_times() to
thread_group_cputime_adjusted(). This name better suggests that
it's a version of thread_group_cputime() that does some stabilization
on the raw cputime values. ie here: scale on top of CFS runtime
stats and bound lower value for monotonicity.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-11-28 17:07:57 +01:00
Frederic Weisbecker
a634f93335 cputime: Move thread_group_cputime() to sched code
thread_group_cputime() is a general cputime API that is not only
used by posix cpu timer. Let's move this helper to sched code.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-11-28 17:07:38 +01:00
Marcelo Tosatti
582b336ec2 sched: add notifier for cross-cpu migrations
Originally from Jeremy Fitzhardinge.

Acked-by: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2012-11-27 23:29:09 -02:00
Eric W. Biederman
4c44aaafa8 userns: Kill task_user_ns
The task_user_ns function hides the fact that it is getting the user
namespace from struct cred on the task.  struct cred may go away as
soon as the rcu lock is released.  This leads to a race where we
can dereference a stale user namespace pointer.

To make it obvious a struct cred is involved kill task_user_ns.

To kill the race modify the users of task_user_ns to only
reference the user namespace while the rcu lock is held.

Cc: Kees Cook <keescook@chromium.org>
Cc: James Morris <james.l.morris@oracle.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2012-11-20 04:17:44 -08:00
Tejun Heo
92fb97487a cgroup: rename ->create/post_create/pre_destroy/destroy() to ->css_alloc/online/offline/free()
Rename cgroup_subsys css lifetime related callbacks to better describe
what their roles are.  Also, update documentation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
2012-11-19 08:13:38 -08:00
Frederic Weisbecker
1017769bd0 vtime: No need to disable irqs on vtime_account()
vtime_account() is only called from irq entry. irqs
are always disabled at this point so we can safely
remove the irq disabling guards on that function.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
2012-11-19 16:41:41 +01:00
Frederic Weisbecker
e3942ba040 vtime: Consolidate a bit the ctx switch code
On ia64 and powerpc, vtime context switch only consists
in flushing system and user pending time, plus a few
arch housekeeping.

Consolidate that into a generic implementation. s390 is
a special case because pending user and system time accounting
there is hard to dissociate. So it's keeping its own implementation.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
2012-11-19 16:41:32 +01:00
Frederic Weisbecker
fd25b4c2f2 vtime: Remove the underscore prefix invasion
Prepending irq-unsafe vtime APIs with underscores was actually
a bad idea as the result is a big mess in the API namespace that
is even waiting to be further extended. Also these helpers
are always called from irq safe callers except kvm. Just
provide a vtime_account_system_irqsafe() for this specific
case so that we can remove the underscore prefix on other
vtime functions.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
2012-11-19 16:40:16 +01:00
Ingo Molnar
ec05a2311c Merge branch 'sched/urgent' into sched/core
Merge in fixes before we queue up dependent bits, to avoid conflicts.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-11-18 09:34:44 +01:00
Paul E. McKenney
4e79752c25 sched: Mark RCU reader in sched_show_task()
When sched_show_task() is invoked from try_to_freeze_tasks(), there is
no RCU read-side critical section, resulting in the following splat:

[  125.780730] ===============================
[  125.780766] [ INFO: suspicious RCU usage. ]
[  125.780804] 3.7.0-rc3+ #988 Not tainted
[  125.780838] -------------------------------
[  125.780875] /home/rafael/src/linux/kernel/sched/core.c:4497 suspicious rcu_dereference_check() usage!
[  125.780946]
[  125.780946] other info that might help us debug this:
[  125.780946]
[  125.781031]
[  125.781031] rcu_scheduler_active = 1, debug_locks = 0
[  125.781087] 4 locks held by s2ram/4211:
[  125.781120]  #0:  (&buffer->mutex){+.+.+.}, at: [<ffffffff811e2acf>] sysfs_write_file+0x3f/0x160
[  125.781233]  #1:  (s_active#94){.+.+.+}, at: [<ffffffff811e2b58>] sysfs_write_file+0xc8/0x160
[  125.781339]  #2:  (pm_mutex){+.+.+.}, at: [<ffffffff81090a81>] pm_suspend+0x81/0x230
[  125.781439]  #3:  (tasklist_lock){.?.?..}, at: [<ffffffff8108feed>] try_to_freeze_tasks+0x2cd/0x3f0
[  125.781543]
[  125.781543] stack backtrace:
[  125.781584] Pid: 4211, comm: s2ram Not tainted 3.7.0-rc3+ #988
[  125.781632] Call Trace:
[  125.781662]  [<ffffffff810a3c73>] lockdep_rcu_suspicious+0x103/0x140
[  125.781719]  [<ffffffff8107cf21>] sched_show_task+0x121/0x180
[  125.781770]  [<ffffffff8108ffb4>] try_to_freeze_tasks+0x394/0x3f0
[  125.781823]  [<ffffffff810903b5>] freeze_kernel_threads+0x25/0x80
[  125.781876]  [<ffffffff81090b65>] pm_suspend+0x165/0x230
[  125.781924]  [<ffffffff8108fa29>] state_store+0x99/0x100
[  125.781975]  [<ffffffff812f5867>] kobj_attr_store+0x17/0x20
[  125.782038]  [<ffffffff811e2b71>] sysfs_write_file+0xe1/0x160
[  125.782091]  [<ffffffff811667a6>] vfs_write+0xc6/0x180
[  125.782138]  [<ffffffff81166ada>] sys_write+0x5a/0xa0
[  125.782185]  [<ffffffff812ff6ae>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[  125.782242]  [<ffffffff81669dd2>] system_call_fastpath+0x16/0x1b

This commit therefore adds the needed RCU read-side critical section.

Reported-by: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-11-16 10:05:58 -08:00
Paul E. McKenney
aac1cda34b Merge branches 'urgent.2012.10.27a', 'doc.2012.11.16a', 'fixes.2012.11.13a', 'srcu.2012.10.27a', 'stall.2012.11.13a', 'tracing.2012.11.08a' and 'idle.2012.10.24a' into HEAD
urgent.2012.10.27a: Fix for RCU user-mode transition (already in -tip).

doc.2012.11.08a: Documentation updates, most notably codifying the
	memory-barrier guarantees inherent to grace periods.

fixes.2012.11.13a: Miscellaneous fixes.

srcu.2012.10.27a: Allow statically allocated and initialized srcu_struct
	structures (courtesy of Lai Jiangshan).

stall.2012.11.13a: Add more diagnostic information to RCU CPU stall
	warnings, also decrease from 60 seconds to 21 seconds.

hotplug.2012.11.08a: Minor updates to CPU hotplug handling.

tracing.2012.11.08a: Improved debugfs tracing, courtesy of Michael Wang.

idle.2012.10.24a: Updates to RCU idle/adaptive-idle handling, including
	a boot parameter that maps normal grace periods to expedited.

Resolved conflict in kernel/rcutree.c due to side-by-side change.
2012-11-16 09:59:58 -08:00
Mike Galbraith
5258f386ea sched/autogroup: Fix crash on reboot when autogroup is disabled
Due to these two commits:

  8323f26ce3 sched: Fix race in task_group()
  800d4d30c8 sched, autogroup: Stop going ahead if autogroup is disabled

... autogroup scheduling's dynamic knobs are wrecked.

With both patches applied, all you have to do to crash a box is
disable autogroup during boot up, then reboot.. boom, NULL pointer
dereference due to 800d4d30 not allowing autogroup to move things,
and 8323f26ce making that the only way to switch runqueues.

Remove most of the (dysfunctional) knobs and turn the remaining
sched_autogroup_enabled knob readonly.

If the user fiddles with cgroups hereafter, once tasks
are moved, autogroup won't mess with them again unless
they call setsid().

No knobs, no glitz, nada, just a cute little thing folks can
turn on if they don't want to muck about with cgroups and/or
systemd.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Xiaotian Feng <xtfeng@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xiaotian Feng <dannyfeng@tencent.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org> # v3.6
Link: http://lkml.kernel.org/r/1351451963.4999.8.camel@maggy.simpson.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-30 10:26:04 +01:00
Frederic Weisbecker
3e1df4f506 cputime: Separate irqtime accounting from generic vtime
vtime_account() doesn't have the same role in
CONFIG_VIRT_CPU_ACCOUNTING and CONFIG_IRQ_TIME_ACCOUNTING.

In the first case it handles time accounting in any context. In
the second case it only handles irq time accounting.

So when vtime_account() is called from outside vtime_account_irq_*()
this call is pointless to CONFIG_IRQ_TIME_ACCOUNTING.

To fix the confusion, change vtime_account() to irqtime_account_irq()
in CONFIG_IRQ_TIME_ACCOUNTING. This way we ensure future account_vtime()
calls won't waste useless cycles in the irqtime APIs.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-10-29 21:31:32 +01:00
Frederic Weisbecker
11113334d1 vtime: Make vtime_account_system() irqsafe
vtime_account_system() currently has only one caller with
vtime_account() which is irq safe.

Now we are going to call it from other places like kvm where
irqs are not always disabled by the time we account the cputime.

So let's make it irqsafe. The arch implementation part is now
prefixed with "__".

vtime_account_idle() arch implementation is prefixed accordingly
to stay consistent.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
2012-10-29 21:31:31 +01:00
Peter Zijlstra
e9c84cb8d5 sched: Describe CFS load-balancer
Add some scribbles on how and why the load-balancer works..

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1341316406.23484.64.camel@twins
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:33 +02:00
Paul Turner
f4e26b120b sched: Introduce temporary FAIR_GROUP_SCHED dependency for load-tracking
While per-entity load-tracking is generally useful, beyond computing shares
distribution, e.g. runnable based load-balance (in progress), governors,
power-management, etc.

These facilities are not yet consumers of this data.  This may be trivially
reverted when the information is required; but avoid paying the overhead for
calculations we will not use until then.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141507.422162369@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:31 +02:00
Paul Turner
5b51f2f80b sched: Make __update_entity_runnable_avg() fast
__update_entity_runnable_avg forms the core of maintaining an entity's runnable
load average.  In this function we charge the accumulated run-time since last
update and handle appropriate decay.  In some cases, e.g. a waking task, this
time interval may be much larger than our period unit.

Fortunately we can exploit some properties of our series to perform decay for a
blocked update in constant time and account the contribution for a running
update in essentially-constant* time.

[*]: For any running entity they should be performing updates at the tick which
gives us a soft limit of 1 jiffy between updates, and we can compute up to a
32 jiffy update in a single pass.

C program to generate the magic constants in the arrays:

  #include <math.h>
  #include <stdio.h>

  #define N 32
  #define WMULT_SHIFT 32

  const long WMULT_CONST = ((1UL << N) - 1);
  double y;

  long runnable_avg_yN_inv[N];
  void calc_mult_inv() {
  	int i;
  	double yn = 0;

  	printf("inverses\n");
  	for (i = 0; i < N; i++) {
  		yn = (double)WMULT_CONST * pow(y, i);
  		runnable_avg_yN_inv[i] = yn;
  		printf("%2d: 0x%8lx\n", i, runnable_avg_yN_inv[i]);
  	}
  	printf("\n");
  }

  long mult_inv(long c, int n) {
  	return (c * runnable_avg_yN_inv[n]) >>  WMULT_SHIFT;
  }

  void calc_yn_sum(int n)
  {
  	int i;
  	double sum = 0, sum_fl = 0, diff = 0;

  	/*
  	 * We take the floored sum to ensure the sum of partial sums is never
  	 * larger than the actual sum.
  	 */
  	printf("sum y^n\n");
  	printf("   %8s  %8s %8s\n", "exact", "floor", "error");
  	for (i = 1; i <= n; i++) {
  		sum = (y * sum + y * 1024);
  		sum_fl = floor(y * sum_fl+ y * 1024);
  		printf("%2d: %8.0f  %8.0f %8.0f\n", i, sum, sum_fl,
  			sum_fl - sum);
  	}
  	printf("\n");
  }

  void calc_conv(long n) {
  	long old_n;
  	int i = -1;

  	printf("convergence (LOAD_AVG_MAX, LOAD_AVG_MAX_N)\n");
  	do {
  		old_n = n;
  		n = mult_inv(n, 1) + 1024;
  		i++;
  	} while (n != old_n);
  	printf("%d> %ld\n", i - 1, n);
  	printf("\n");
  }

  void main() {
  	y = pow(0.5, 1/(double)N);
  	calc_mult_inv();
  	calc_conv(1024);
  	calc_yn_sum(N);
  }

[ Compile with -lm ]
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141507.277808946@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:30 +02:00
Paul Turner
f269ae0469 sched: Update_cfs_shares at period edge
Now that our measurement intervals are small (~1ms) we can amortize the posting
of update_shares() to be about each period overflow.  This is a large cost
saving for frequently switching tasks.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141507.200772172@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:29 +02:00
Paul Turner
48a1675323 sched: Refactor update_shares_cpu() -> update_blocked_avgs()
Now that running entities maintain their own load-averages the work we must do
in update_shares() is largely restricted to the periodic decay of blocked
entities.  This allows us to be a little less pessimistic regarding our
occupancy on rq->lock and the associated rq->clock updates required.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141507.133999170@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:28 +02:00
Paul Turner
82958366cf sched: Replace update_shares weight distribution with per-entity computation
Now that the machinery in place is in place to compute contributed load in a
bottom up fashion; replace the shares distribution code within update_shares()
accordingly.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141507.061208672@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:28 +02:00
Paul Turner
f1b17280ef sched: Maintain runnable averages across throttled periods
With bandwidth control tracked entities may cease execution according to user
specified bandwidth limits.  Charging this time as either throttled or blocked
however, is incorrect and would falsely skew in either direction.

What we actually want is for any throttled periods to be "invisible" to
load-tracking as they are removed from the system for that interval and
contribute normally otherwise.

Do this by moderating the progression of time to omit any periods in which the
entity belonged to a throttled hierarchy.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.998912151@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:27 +02:00
Paul Turner
bb17f65571 sched: Normalize tg load contributions against runnable time
Entities of equal weight should receive equitable distribution of cpu time.
This is challenging in the case of a task_group's shares as execution may be
occurring on multiple cpus simultaneously.

To handle this we divide up the shares into weights proportionate with the load
on each cfs_rq.  This does not however, account for the fact that the sum of
the parts may be less than one cpu and so we need to normalize:
  load(tg) = min(runnable_avg(tg), 1) * tg->shares
Where runnable_avg is the aggregate time in which the task_group had runnable
children.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.930124292@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:26 +02:00
Paul Turner
8165e145ce sched: Compute load contribution by a group entity
Unlike task entities who have a fixed weight, group entities instead own a
fraction of their parenting task_group's shares as their contributed weight.

Compute this fraction so that we can correctly account hierarchies and shared
entity nodes.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.855074415@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:25 +02:00
Paul Turner
c566e8e9e4 sched: Aggregate total task_group load
Maintain a global running sum of the average load seen on each cfs_rq belonging
to each task group so that it may be used in calculating an appropriate
shares:weight distribution.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.792901086@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:24 +02:00
Paul Turner
aff3e49884 sched: Account for blocked load waking back up
When a running entity blocks we migrate its tracked load to
cfs_rq->blocked_runnable_avg.  In the sleep case this occurs while holding
rq->lock and so is a natural transition.  Wake-ups however, are potentially
asynchronous in the presence of migration and so special care must be taken.

We use an atomic counter to track such migrated load, taking care to match this
with the previously introduced decay counters so that we don't migrate too much
load.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.726077467@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:23 +02:00
Paul Turner
0a74bef8be sched: Add an rq migration call-back to sched_class
Since we are now doing bottom up load accumulation we need explicit
notification when a task has been re-parented so that the old hierarchy can be
updated.

Adds: migrate_task_rq(struct task_struct *p, int next_cpu)

(The alternative is to do this out of __set_task_cpu, but it was suggested that
this would be a cleaner encapsulation.)

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.660023400@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:23 +02:00
Paul Turner
9ee474f556 sched: Maintain the load contribution of blocked entities
We are currently maintaining:

  runnable_load(cfs_rq) = \Sum task_load(t)

For all running children t of cfs_rq.  While this can be naturally updated for
tasks in a runnable state (as they are scheduled); this does not account for
the load contributed by blocked task entities.

This can be solved by introducing a separate accounting for blocked load:

  blocked_load(cfs_rq) = \Sum runnable(b) * weight(b)

Obviously we do not want to iterate over all blocked entities to account for
their decay, we instead observe that:

  runnable_load(t) = \Sum p_i*y^i

and that to account for an additional idle period we only need to compute:

  y*runnable_load(t).

This means that we can compute all blocked entities at once by evaluating:

  blocked_load(cfs_rq)` = y * blocked_load(cfs_rq)

Finally we maintain a decay counter so that when a sleeping entity re-awakens
we can determine how much of its load should be removed from the blocked sum.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.585389902@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:22 +02:00
Paul Turner
2dac754e10 sched: Aggregate load contributed by task entities on parenting cfs_rq
For a given task t, we can compute its contribution to load as:

  task_load(t) = runnable_avg(t) * weight(t)

On a parenting cfs_rq we can then aggregate:

  runnable_load(cfs_rq) = \Sum task_load(t), for all runnable children t

Maintain this bottom up, with task entities adding their contributed load to
the parenting cfs_rq sum.  When a task entity's load changes we add the same
delta to the maintained sum.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.514678907@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:21 +02:00
Ben Segall
18bf2805d9 sched: Maintain per-rq runnable averages
Since runqueues do not have a corresponding sched_entity we instead embed a
sched_avg structure directly.

Signed-off-by: Ben Segall <bsegall@google.com>
Reviewed-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.442637130@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:20 +02:00
Paul Turner
9d85f21c94 sched: Track the runnable average on a per-task entity basis
Instead of tracking averaging the load parented by a cfs_rq, we can track
entity load directly. With the load for a given cfs_rq then being the sum
of its children.

To do this we represent the historical contribution to runnable average
within each trailing 1024us of execution as the coefficients of a
geometric series.

We can express this for a given task t as:

  runnable_sum(t) = \Sum u_i * y^i, runnable_avg_period(t) = \Sum 1024 * y^i
  load(t) = weight_t * runnable_sum(t) / runnable_avg_period(t)

Where: u_i is the usage in the last i`th 1024us period (approximately 1ms)
~ms and y is chosen such that y^k = 1/2.  We currently choose k to be 32 which
roughly translates to about a sched period.

Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.372695337@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24 10:27:18 +02:00
Paul E. McKenney
b637a328bd rcu: Print remote CPU's stacks in stall warnings
The RCU CPU stall warnings rely on trigger_all_cpu_backtrace() to
do NMI-based dump of the stack traces of all CPUs.  Unfortunately, a
number of architectures do not implement trigger_all_cpu_backtrace(), in
which case RCU falls back to just dumping the stack of the running CPU.
This is unhelpful in the case where the running CPU has detected that
some other CPU has stalled.

This commit therefore makes the running CPU dump the stacks of the
tasks running on the stalled CPUs.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-10-23 14:55:25 -07:00
Frederic Weisbecker
4d9a5d4319 rcu: Remove rcu_switch()
It's only there to call rcu_user_hooks_switch(). Let's
just call rcu_user_hooks_switch() directly, we don't need this
function in the middle.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-10-23 14:54:06 -07:00
Ingo Molnar
8ed92e51f9 sched: Add WAKEUP_PREEMPTION feature flag, on by default
As per the recent discussion with Mike and Linus, make it easier to
test with/without this feature. No change in default behavior.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-izoxq4haeg4mTognnDbwcevt@git.kernel.org
2012-10-16 10:05:27 +02:00
Linus Torvalds
0588f1f934 Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar:
 "A CPU hotplug related crash fix and a nohz accounting fixlet."

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Update sched_domains_numa_masks[][] when new cpus are onlined
  sched: Ensure 'sched_domains_numa_levels' is safe to use in other functions
  nohz: Fix one jiffy count too far in idle cputime
2012-10-12 22:13:05 +09:00
Linus Torvalds
8213a2f3ee Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal
Pull pile 2 of execve and kernel_thread unification work from Al Viro:
 "Stuff in there: kernel_thread/kernel_execve/sys_execve conversions for
  several more architectures plus assorted signal fixes and cleanups.

  There'll be more (in particular, real fixes for the alpha
  do_notify_resume() irq mess)..."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal: (43 commits)
  alpha: don't open-code trace_report_syscall_{enter,exit}
  Uninclude linux/freezer.h
  m32r: trim masks
  avr32: trim masks
  tile: don't bother with SIGTRAP in setup_frame
  microblaze: don't bother with SIGTRAP in setup_rt_frame()
  mn10300: don't bother with SIGTRAP in setup_frame()
  frv: no need to raise SIGTRAP in setup_frame()
  x86: get rid of duplicate code in case of CONFIG_VM86
  unicore32: remove pointless test
  h8300: trim _TIF_WORK_MASK
  parisc: decide whether to go to slow path (tracesys) based on thread flags
  parisc: don't bother looping in do_signal()
  parisc: fix double restarts
  bury the rest of TIF_IRET
  sanitize tsk_is_polling()
  bury _TIF_RESTORE_SIGMASK
  unicore32: unobfuscate _TIF_WORK_MASK
  mips: NOTIFY_RESUME is not needed in TIF masks
  mips: merge the identical "return from syscall" per-ABI code
  ...

Conflicts:
	arch/arm/include/asm/thread_info.h
2012-10-12 10:49:08 +09:00
Tang Chen
301a5cba28 sched: Update sched_domains_numa_masks[][] when new cpus are onlined
Once array sched_domains_numa_masks[] []is defined, it is never updated.

When a new cpu on a new node is onlined, the coincident member in
sched_domains_numa_masks[][] is not initialized, and all the masks are 0.
As a result, the build_overlap_sched_groups() will initialize a NULL
sched_group for the new cpu on the new node, which will lead to kernel panic:

[ 3189.403280] Call Trace:
[ 3189.403286]  [<ffffffff8106c36f>] warn_slowpath_common+0x7f/0xc0
[ 3189.403289]  [<ffffffff8106c3ca>] warn_slowpath_null+0x1a/0x20
[ 3189.403292]  [<ffffffff810b1d57>] build_sched_domains+0x467/0x470
[ 3189.403296]  [<ffffffff810b2067>] partition_sched_domains+0x307/0x510
[ 3189.403299]  [<ffffffff810b1ea2>] ? partition_sched_domains+0x142/0x510
[ 3189.403305]  [<ffffffff810fcc93>] cpuset_update_active_cpus+0x83/0x90
[ 3189.403308]  [<ffffffff810b22a8>] cpuset_cpu_active+0x38/0x70
[ 3189.403316]  [<ffffffff81674b87>] notifier_call_chain+0x67/0x150
[ 3189.403320]  [<ffffffff81664647>] ? native_cpu_up+0x18a/0x1b5
[ 3189.403328]  [<ffffffff810a044e>] __raw_notifier_call_chain+0xe/0x10
[ 3189.403333]  [<ffffffff81070470>] __cpu_notify+0x20/0x40
[ 3189.403337]  [<ffffffff8166663e>] _cpu_up+0xe9/0x131
[ 3189.403340]  [<ffffffff81666761>] cpu_up+0xdb/0xee
[ 3189.403348]  [<ffffffff8165667c>] store_online+0x9c/0xd0
[ 3189.403355]  [<ffffffff81437640>] dev_attr_store+0x20/0x30
[ 3189.403361]  [<ffffffff8124aa63>] sysfs_write_file+0xa3/0x100
[ 3189.403368]  [<ffffffff811ccbe0>] vfs_write+0xd0/0x1a0
[ 3189.403371]  [<ffffffff811ccdb4>] sys_write+0x54/0xa0
[ 3189.403375]  [<ffffffff81679c69>] system_call_fastpath+0x16/0x1b
[ 3189.403377] ---[ end trace 1e6cf85d0859c941 ]---
[ 3189.403398] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018

This patch registers a new notifier for cpu hotplug notify chain, and
updates sched_domains_numa_masks every time a new cpu is onlined or offlined.

Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
[ fixed compile warning ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1348578751-16904-3-git-send-email-tangchen@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-05 13:54:48 +02:00
Tang Chen
5f7865f3e4 sched: Ensure 'sched_domains_numa_levels' is safe to use in other functions
We should temporarily reset 'sched_domains_numa_levels' to 0 after
it is reset to 'level' in sched_init_numa(). If it fails to allocate
memory for array sched_domains_numa_masks[][], the array will contain
less then 'level' members. This could be dangerous when we use it to
iterate array sched_domains_numa_masks[][] in other functions.

This patch set sched_domains_numa_levels to 0 before initializing
array sched_domains_numa_masks[][], and reset it to 'level' when
sched_domains_numa_masks[][] is fully initialized.

Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1348578751-16904-2-git-send-email-tangchen@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-05 13:54:46 +02:00
Linus Torvalds
0b981cb94b Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler changes from Ingo Molnar:
 "Continued quest to clean up and enhance the cputime code by Frederic
  Weisbecker, in preparation for future tickless kernel features.

  Other than that, smallish changes."

Fix up trivial conflicts due to additions next to each other in arch/{x86/}Kconfig

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
  cputime: Make finegrained irqtime accounting generally available
  cputime: Gather time/stats accounting config options into a single menu
  ia64: Reuse system and user vtime accounting functions on task switch
  ia64: Consolidate user vtime accounting
  vtime: Consolidate system/idle context detection
  cputime: Use a proper subsystem naming for vtime related APIs
  sched: cpu_power: enable ARCH_POWER
  sched/nohz: Clean up select_nohz_load_balancer()
  sched: Fix load avg vs. cpu-hotplug
  sched: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW
  sched: Fix nohz_idle_balance()
  sched: Remove useless code in yield_to()
  sched: Add time unit suffix to sched sysctl knobs
  sched/debug: Limit sd->*_idx range on sysctl
  sched: Remove AFFINE_WAKEUPS feature flag
  s390: Remove leftover account_tick_vtime() header
  cputime: Consolidate vtime handling on context switch
  sched: Move cputime code to its own file
  cputime: Generalize CONFIG_VIRT_CPU_ACCOUNTING
  tile: Remove SD_PREFER_LOCAL leftover
  ...
2012-10-01 10:43:39 -07:00
Al Viro
16a8016372 sanitize tsk_is_polling()
Make default just return 0.  The current default (checking
TIF_POLLING_NRFLAG) is taken to architectures that need it;
ones that don't do polling in their idle threads don't need
to defined TIF_POLLING_NRFLAG at all.

ia64 defined both TS_POLLING (used by its tsk_is_polling())
and TIF_POLLING_NRFLAG (not used at all).  Killed the latter...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-10-01 09:58:13 -04:00
Frederic Weisbecker
20ab65e33f rcu: Exit RCU extended QS on user preemption
When exceptions or irq are about to resume userspace, if
the task needs to be rescheduled, the arch low level code
calls schedule() directly.

If we call it, it is because we have the TIF_RESCHED flag:

- It can be set after random local calls to set_need_resched()
(RCU, drm, ...)

- A wake up happened and the CPU needs preemption. This can
  happen in several ways:

    * Remotely: the remote waking CPU has set TIF_RESCHED and send the
      wakee an IPI to schedule the new task.
    * Remotely enqueued: the remote waking CPU sends an IPI to the target
      and the wake up is made by the target.
    * Locally: waking CPU == wakee CPU and the wakeup is done locally.
      set_need_resched() is called without IPI.

In the case of local and remotely enqueued wake ups, the tick can
be restarted when we enqueue the new task and RCU can exit the
extended quiescent state at the same time. Then by the time we reach
irq exit path and we call schedule, we are not in RCU user mode.

But if we call schedule() only because something called set_need_resched(),
RCU may still be in user mode when we reach schedule.

Also if a wake up is done remotely, the CPU might see the TIF_RESCHED
flag and call schedule while the IPI has not yet happen to restart the
tick and exit RCU user mode.

We need to manually protect against these corner cases.

Create a new API schedule_user() that calls schedule() inside
rcu_user_exit()-rcu_user_enter() in order to protect it. Archs
will need to rely on it now to implement user preemption safely.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-09-26 15:47:11 +02:00
Frederic Weisbecker
90a340ed53 rcu: Exit RCU extended QS on kernel preemption after irq/exception
When an exception or an irq exits, and we are going to resume into
interrupted kernel code, the low level architecture code calls
preempt_schedule_irq() if there is a need to reschedule.

If the interrupt/exception occured between a call to rcu_user_enter()
(from syscall exit, exception exit, do_notify_resume exit, ...) and
a real resume to userspace (iret,...), preempt_schedule_irq() can be
called whereas RCU thinks we are in userspace. But preempt_schedule_irq()
is going to run kernel code and may be some RCU read side critical
section. We must exit the userspace extended quiescent state before
we call it.

To solve this, just call rcu_user_exit() in the beginning of
preempt_schedule_irq().

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-09-26 15:47:09 +02:00
Frederic Weisbecker
04e7e95153 rcu: Switch task's syscall hooks on context switch
Clear the syscalls hook of a task when it's scheduled out so that if
the task migrates, it doesn't run the syscall slow path on a CPU
that might not need it.

Also set the syscalls hook on the next task if needed.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2012-09-26 15:47:02 +02:00
Paul E. McKenney
593d1006cd Merge remote-tracking branch 'tip/core/rcu' into next.2012.09.25b
Resolved conflict in kernel/sched/core.c using Peter Zijlstra's
approach from https://lkml.org/lkml/2012/9/5/585.
2012-09-25 10:03:56 -07:00
Frederic Weisbecker
a7e1a9e3af vtime: Consolidate system/idle context detection
Move the code that finds out to which context we account the
cputime into generic layer.

Archs that consider the whole time spent in the idle task as idle
time (ia64, powerpc) can rely on the generic vtime_account()
and implement vtime_account_system() and vtime_account_idle(),
letting the generic code to decide when to call which API.

Archs that have their own meaning of idle time, such as s390
that only considers the time spent in CPU low power mode as idle
time, can just override vtime_account().

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
2012-09-25 15:42:37 +02:00
Frederic Weisbecker
bf9fae9f5e cputime: Use a proper subsystem naming for vtime related APIs
Use a naming based on vtime as a prefix for virtual based
cputime accounting APIs:

- account_system_vtime() -> vtime_account()
- account_switch_vtime() -> vtime_task_switch()

It makes it easier to allow for further declension such
as vtime_account_system(), vtime_account_idle(), ... if we
want to find out the context we account to from generic code.

This also make it better to know on which subsystem these APIs
refer to.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
2012-09-25 15:31:31 +02:00
Peter Zijlstra
5d18023294 sched: Fix load avg vs cpu-hotplug
Rabik and Paul reported two different issues related to the same few
lines of code.

Rabik's issue is that the nr_uninterruptible migration code is wrong in
that he sees artifacts due to this (Rabik please do expand in more
detail).

Paul's issue is that this code as it stands relies on us using
stop_machine() for unplug, we all would like to remove this assumption
so that eventually we can remove this stop_machine() usage altogether.

The only reason we'd have to migrate nr_uninterruptible is so that we
could use for_each_online_cpu() loops in favour of
for_each_possible_cpu() loops, however since nr_uninterruptible() is the
only such loop and its using possible lets not bother at all.

The problem Rabik sees is (probably) caused by the fact that by
migrating nr_uninterruptible we screw rq->calc_load_active for both rqs
involved.

So don't bother with fancy migration schemes (meaning we now have to
keep using for_each_possible_cpu()) and instead fold any nr_active delta
after we migrate all tasks away to make sure we don't have any skewed
nr_active accounting.

[ paulmck: Move call to calc_load_migration to CPU_DEAD to avoid
miscounting noted by Rakib. ]

Reported-by: Rakib Mullick <rakib.mullick@gmail.com>
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
2012-09-23 07:43:56 -07:00
Linus Torvalds
37407ea7f9 Revert "sched: Improve scalability via 'CPU buddies', which withstand random perturbations"
This reverts commit 970e178985.

Nikolay Ulyanitsky reported thatthe 3.6-rc5 kernel has a 15-20%
performance drop on PostgreSQL 9.2 on his machine (running "pgbench").

Borislav Petkov was able to reproduce this, and bisected it to this
commit 970e178985 ("sched: Improve scalability via 'CPU buddies' ...")
apparently because the new single-idle-buddy model simply doesn't find
idle CPU's to reschedule on aggressively enough.

Mike Galbraith suspects that it is likely due to the user-mode spinlocks
in PostgreSQL not reacting well to preemption, but we don't really know
the details - I'll just revert the commit for now.

There are hopefully other approaches to improve scheduler scalability
without it causing these kinds of downsides.

Reported-by: Nikolay Ulyanitsky <lystor@gmail.com>
Bisected-by: Borislav Petkov <bp@alien8.de>
Acked-by: Mike Galbraith <efault@gmx.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-09-16 12:29:43 -07:00
Vincent Guittot
bc2a27cd27 sched: cpu_power: enable ARCH_POWER
Heteregeneous ARM platform uses arch_scale_freq_power function
to reflect the relative capacity of each core

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1341826026-6504-6-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-13 16:52:06 +02:00
Alex Shi
c1cc017c59 sched/nohz: Clean up select_nohz_load_balancer()
There is no load_balancer to be selected now. It just sets the
state of the nohz tick to stop.

So rename the function, pass the 'cpu' as a parameter and then
remove the useless call from tick_nohz_restart_sched_tick().

[ s/set_nohz_tick_stopped/nohz_balance_enter_idle/g
  s/clear_nohz_tick_stopped/nohz_balance_exit_idle/g ]
Signed-off-by: Alex Shi <alex.shi@intel.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1347261059-24747-1-git-send-email-alex.shi@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-13 16:52:05 +02:00
Peter Zijlstra
08bedae1d0 sched: Fix load avg vs. cpu-hotplug
Commit f319da0c68 ("sched: Fix load avg vs cpu-hotplug") was an
incomplete fix:

In particular, the problem is that at the point it calls
calc_load_migrate() nr_running := 1 (the stopper thread), so move the
call to CPU_DEAD where we're sure that nr_running := 0.

Also note that we can call calc_load_migrate() without serialization, we
know the state of rq is stable since its cpu is dead, and we modify the
global state using appropriate atomic ops.

Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1346882630.2600.59.camel@twins
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-13 16:52:05 +02:00
Peter Zijlstra
f3e9478674 sched: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW
Now that the last architecture to use this has stopped doing so (ARM,
thanks Catalin!) we can remove this complexity from the scheduler
core.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Link: http://lkml.kernel.org/n/tip-g9p2a1w81xxbrze25v9zpzbf@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-13 16:52:04 +02:00
Vincent Guittot
5ed4f1d96d sched: Fix nohz_idle_balance()
On tickless systems, one CPU runs load balance for all idle CPUs.

The cpu_load of this CPU is updated before starting the load balance
of each other idle CPUs. We should instead update the cpu_load of
the balance_cpu.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Venkatesh Pallipadi <venki@google.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1347509486-8688-1-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-13 16:52:03 +02:00
Michael Wang
38b8dd6f87 sched: Remove useless code in yield_to()
It's impossible to enter the else branch if we have set
skip_clock_update in task_yield_fair(), as yield_to_task_fair()
 will directly return true after invoke task_yield_fair().

Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Acked-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4FF2925A.9060005@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-04 14:31:42 +02:00
Namhyung Kim
201c373e8e sched/debug: Limit sd->*_idx range on sysctl
Various sd->*_idx's are used for refering the rq's load average table
when selecting a cpu to run.  However they can be set to any number
with sysctl knobs so that it can crash the kernel if something bad is
given. Fix it by limiting them into the actual range.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1345104204-8317-1-git-send-email-namhyung@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-04 14:31:32 +02:00
Namhyung Kim
c751134ef8 sched: Remove AFFINE_WAKEUPS feature flag
Commit beac4c7e4a ("sched: Remove AFFINE_WAKEUPS feature") removed
use of the flag but left the definition. Get rid of it.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Link: http://lkml.kernel.org/r/1345090865-20851-1-git-send-email-namhyung@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-04 14:31:31 +02:00
Ingo Molnar
59f979455d Merge branch 'sched/urgent' into sched/core
Merge in the current fixes branch, we are going to apply dependent patches.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-04 14:31:00 +02:00
Randy Dunlap
9450d57eab sched: Fix kernel-doc warnings in kernel/sched/fair.c
Fix two kernel-doc warnings in kernel/sched/fair.c:

  Warning(kernel/sched/fair.c:3660): Excess function parameter 'cpus' description in 'update_sg_lb_stats'
  Warning(kernel/sched/fair.c:3806): Excess function parameter 'cpus' description in 'update_sd_lb_stats'

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/50303714.3090204@xenotime.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-04 14:30:49 +02:00
Peter Boonstoppel
a4c96ae319 sched: Unthrottle rt runqueues in __disable_runtime()
migrate_tasks() uses _pick_next_task_rt() to get tasks from the
real-time runqueues to be migrated. When rt_rq is throttled
_pick_next_task_rt() won't return anything, in which case
migrate_tasks() can't move all threads over and gets stuck in an
infinite loop.

Instead unthrottle rt runqueues before migrating tasks.

Additionally: move unthrottle_offline_cfs_rqs() to rq_offline_fair()

Signed-off-by: Peter Boonstoppel <pboonstoppel@nvidia.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/5FBF8E85CA34454794F0F7ECBA79798F379D3648B7@HQMAIL04.nvidia.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-04 14:30:30 +02:00
Peter Zijlstra
f319da0c68 sched: Fix load avg vs cpu-hotplug
Rabik and Paul reported two different issues related to the same few
lines of code.

Rabik's issue is that the nr_uninterruptible migration code is wrong in
that he sees artifacts due to this (Rabik please do expand in more
detail).

Paul's issue is that this code as it stands relies on us using
stop_machine() for unplug, we all would like to remove this assumption
so that eventually we can remove this stop_machine() usage altogether.

The only reason we'd have to migrate nr_uninterruptible is so that we
could use for_each_online_cpu() loops in favour of
for_each_possible_cpu() loops, however since nr_uninterruptible() is the
only such loop and its using possible lets not bother at all.

The problem Rabik sees is (probably) caused by the fact that by
migrating nr_uninterruptible we screw rq->calc_load_active for both rqs
involved.

So don't bother with fancy migration schemes (meaning we now have to
keep using for_each_possible_cpu()) and instead fold any nr_active delta
after we migrate all tasks away to make sure we don't have any skewed
nr_active accounting.

Reported-by: Rakib Mullick <rakib.mullick@gmail.com>
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1345454817.23018.27.camel@twins
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-09-04 14:30:18 +02:00
Linus Torvalds
53795ced6e Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar.

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Fix migration thread runtime bogosity
  sched,rt: fix isolated CPUs leaving root_task_group indefinitely throttled
  sched,cgroup: Fix up task_groups list
  sched: fix divide by zero at {thread_group,task}_times
  sched, cgroup: Reduce rq->lock hold times for large cgroup hierarchies
2012-08-20 10:35:05 -07:00
Frederic Weisbecker
baa36046d0 cputime: Consolidate vtime handling on context switch
The archs that implement virtual cputime accounting all
flush the cputime of a task when it gets descheduled
and sometimes set up some ground initialization for the
next task to account its cputime.

These archs all put their own hooks in their context
switch callbacks and handle the off-case themselves.

Consolidate this by creating a new account_switch_vtime()
callback called in generic code right after a context switch
and that these archs must implement to flush the prev task
cputime and initialize the next task cputime related state.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
2012-08-20 13:05:28 +02:00
Frederic Weisbecker
73fbec6044 sched: Move cputime code to its own file
Extract cputime code from the giant sched/core.c and
put it in its own file. This make it easier to deal with
this particular area and de-bloat a bit more core.c

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
2012-08-20 13:05:17 +02:00
Alex Shi
f03542a701 sched: recover SD_WAKE_AFFINE in select_task_rq_fair and code clean up
Since power saving code was removed from sched now, the implement
code is out of service in this function, and even pollute other logical.
like, 'want_sd' never has chance to be set '0', that remove the effect
of SD_WAKE_AFFINE here.

So, clean up the obsolete code, includes SD_PREFER_LOCAL.

Signed-off-by: Alex Shi <alex.shi@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/5028F431.6000306@intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-08-13 19:02:05 +02:00
Michael Wang
78feefc512 sched: using dst_rq instead of this_rq during load balance
As we already have dst_rq in lb_env, using or changing "this_rq" do not
make sense.

This patch will replace "this_rq" with dst_rq in load_balance, and we
don't need to change "this_rq" while process LBF_SOME_PINNED any more.

Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/501F8357.3070102@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-08-13 18:58:15 +02:00
Pekka Enberg
edde96eafc sched: Document schedule() entry points
This patch adds a comment on top of the schedule() function to explain
to scheduler newbies how the main scheduler function is entered.

Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Explained-by: Ingo Molnar <mingo@kernel.org>
Explained-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1344070187-2420-1-git-send-email-penberg@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-08-13 18:58:15 +02:00
Borislav Petkov
532b1858c5 sched: Fix __sched_period comment
It should be sched_nr_latency so fix it before it annoys me more.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1344435364-18632-1-git-send-email-bp@amd64.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-08-13 18:58:15 +02:00
Thomas Gleixner
a4133765c1 Merge branch 'sched/urgent' into sched/core 2012-08-13 18:56:46 +02:00
Mike Galbraith
8f6189684e sched: Fix migration thread runtime bogosity
Make stop scheduler class do the same accounting as other classes,

Migration threads can be caught in the act while doing exec balancing,
leading to the below due to use of unmaintained ->se.exec_start.  The
load that triggered this particular instance was an apparently out of
control heavily threaded application that does system monitoring in
what equated to an exec bomb, with one of the VERY frequently migrated
tasks being ps.

%CPU   PID USER     CMD
99.3    45 root     [migration/10]
97.7    53 root     [migration/12]
97.0    57 root     [migration/13]
90.1    49 root     [migration/11]
89.6    65 root     [migration/15]
88.7    17 root     [migration/3]
80.4    37 root     [migration/8]
78.1    41 root     [migration/9]
44.2    13 root     [migration/2]

Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1344051854.6739.19.camel@marge.simpson.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-08-13 18:41:55 +02:00
Mike Galbraith
e221d028bb sched,rt: fix isolated CPUs leaving root_task_group indefinitely throttled
Root task group bandwidth replenishment must service all CPUs, regardless of
where the timer was last started, and regardless of the isolation mechanism,
lest 'Quoth the Raven, "Nevermore"' become rt scheduling policy.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1344326558.6968.25.camel@marge.simpson.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-08-13 18:41:55 +02:00
Mike Galbraith
35cf4e50b1 sched,cgroup: Fix up task_groups list
With multiple instances of task_groups, for_each_rt_rq() is a noop,
no task groups having been added to the rt.c list instance.  This
renders __enable/disable_runtime() and print_rt_stats() noop, the
user (non) visible effect being that rt task groups are missing in
/proc/sched_debug.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: stable@kernel.org # v3.3+
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1344308413.6846.7.camel@marge.simpson.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-08-13 18:41:54 +02:00
Stanislaw Gruszka
bea6832cc8 sched: fix divide by zero at {thread_group,task}_times
On architectures where cputime_t is 64 bit type, is possible to trigger
divide by zero on do_div(temp, (__force u32) total) line, if total is a
non zero number but has lower 32 bit's zeroed. Removing casting is not
a good solution since some do_div() implementations do cast to u32
internally.

This problem can be triggered in practice on very long lived processes:

  PID: 2331   TASK: ffff880472814b00  CPU: 2   COMMAND: "oraagent.bin"
   #0 [ffff880472a51b70] machine_kexec at ffffffff8103214b
   #1 [ffff880472a51bd0] crash_kexec at ffffffff810b91c2
   #2 [ffff880472a51ca0] oops_end at ffffffff814f0b00
   #3 [ffff880472a51cd0] die at ffffffff8100f26b
   #4 [ffff880472a51d00] do_trap at ffffffff814f03f4
   #5 [ffff880472a51d60] do_divide_error at ffffffff8100cfff
   #6 [ffff880472a51e00] divide_error at ffffffff8100be7b
      [exception RIP: thread_group_times+0x56]
      RIP: ffffffff81056a16  RSP: ffff880472a51eb8  RFLAGS: 00010046
      RAX: bc3572c9fe12d194  RBX: ffff880874150800  RCX: 0000000110266fad
      RDX: 0000000000000000  RSI: ffff880472a51eb8  RDI: 001038ae7d9633dc
      RBP: ffff880472a51ef8   R8: 00000000b10a3a64   R9: ffff880874150800
      R10: 00007fcba27ab680  R11: 0000000000000202  R12: ffff880472a51f08
      R13: ffff880472a51f10  R14: 0000000000000000  R15: 0000000000000007
      ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
   #7 [ffff880472a51f00] do_sys_times at ffffffff8108845d
   #8 [ffff880472a51f40] sys_times at ffffffff81088524
   #9 [ffff880472a51f80] system_call_fastpath at ffffffff8100b0f2
      RIP: 0000003808caac3a  RSP: 00007fcba27ab6d8  RFLAGS: 00000202
      RAX: 0000000000000064  RBX: ffffffff8100b0f2  RCX: 0000000000000000
      RDX: 00007fcba27ab6e0  RSI: 000000000076d58e  RDI: 00007fcba27ab6e0
      RBP: 00007fcba27ab700   R8: 0000000000000020   R9: 000000000000091b
      R10: 00007fcba27ab680  R11: 0000000000000202  R12: 00007fff9ca41940
      R13: 0000000000000000  R14: 00007fcba27ac9c0  R15: 00007fff9ca41940
      ORIG_RAX: 0000000000000064  CS: 0033  SS: 002b

Cc: stable@vger.kernel.org
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120808092714.GA3580@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-08-13 18:41:54 +02:00
Peter Zijlstra
a35b6466aa sched, cgroup: Reduce rq->lock hold times for large cgroup hierarchies
Peter Portante reported that for large cgroup hierarchies (and or on
large CPU counts) we get immense lock contention on rq->lock and stuff
stops working properly.

His workload was a ton of processes, each in their own cgroup,
everybody idling except for a sporadic wakeup once every so often.

It was found that:

  schedule()
    idle_balance()
      load_balance()
        local_irq_save()
        double_rq_lock()
        update_h_load()
          walk_tg_tree(tg_load_down)
            tg_load_down()

Results in an entire cgroup hierarchy walk under rq->lock for every
new-idle balance and since new-idle balance isn't throttled this
results in a lot of work while holding the rq->lock.

This patch does two things, it removes the work from under rq->lock
based on the good principle of race and pray which is widely employed
in the load-balancer as a whole. And secondly it throttles the
update_h_load() calculation to max once per jiffy.

I considered excluding update_h_load() for new-idle balance
all-together, but purely relying on regular balance passes to update
this data might not work out under some rare circumstances where the
new-idle busiest isn't the regular busiest for a while (unlikely, but
a nightmare to debug if someone hits it and suffers).

Cc: pjt@google.com
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Reported-by: Peter Portante <pportant@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-aaarrzfpnaam7pqrekofu8a6@git.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-08-13 18:41:54 +02:00
Linus Torvalds
fcc1d2a9ce Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar:
 "Fixes and two late cleanups"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/cleanups: Add load balance cpumask pointer to 'struct lb_env'
  sched: Fix comment about PREEMPT_ACTIVE bit location
  sched: Fix minor code style issues
  sched: Use task_rq_unlock() in __sched_setscheduler()
  sched/numa: Add SD_PERFER_SIBLING to CPU domain
2012-08-03 10:58:13 -07:00
Linus Torvalds
bca1a5c0ea Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf updates from Ingo Molnar:
 "The biggest changes are Intel Nehalem-EX PMU uncore support, uprobes
  updates/cleanups/fixes from Oleg and diverse tooling updates (mostly
  fixes) now that Arnaldo is back from vacation."

* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (40 commits)
  uprobes: __replace_page() needs munlock_vma_page()
  uprobes: Rename vma_address() and make it return "unsigned long"
  uprobes: Fix register_for_each_vma()->vma_address() check
  uprobes: Introduce vaddr_to_offset(vma, vaddr)
  uprobes: Teach build_probe_list() to consider the range
  uprobes: Remove insert_vm_struct()->uprobe_mmap()
  uprobes: Remove copy_vma()->uprobe_mmap()
  uprobes: Fix overflow in vma_address()/find_active_uprobe()
  uprobes: Suppress uprobe_munmap() from mmput()
  uprobes: Uprobe_mmap/munmap needs list_for_each_entry_safe()
  uprobes: Clean up and document write_opcode()->lock_page(old_page)
  uprobes: Kill write_opcode()->lock_page(new_page)
  uprobes: __replace_page() should not use page_address_in_vma()
  uprobes: Don't recheck vma/f_mapping in write_opcode()
  perf/x86: Fix missing struct before structure name
  perf/x86: Fix format definition of SNB-EP uncore QPI box
  perf/x86: Make bitfield unsigned
  perf/x86: Fix LLC-* and node-* events on Intel SandyBridge
  perf/x86: Add Intel Nehalem-EX uncore support
  perf/x86: Fix typo in format definition of uncore PCU filter
  ...
2012-07-31 15:34:13 -07:00
Michael Wang
b9403130a5 sched/cleanups: Add load balance cpumask pointer to 'struct lb_env'
With this patch struct ld_env will have a pointer of the load balancing
cpumask and we don't need to pass a cpumask around anymore.

Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4FFE8665.3080705@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-31 17:00:16 +02:00
Andrew Vagin
895dd92c03 sched: Deliver sched_switch events to the current task
Otherwise they can't be filtered for a defined task:

  perf record -e sched:sched_switch ./foo

This command doesn't report any events without this patch.

I think it isn't a security concern if someone knows who will
be executed next - this can already be observed by polling /proc
state. By default perf is disabled for non-root users in any case.

I need these events for profiling sleep times.  sched_switch is used for
getting callchains and sched_stat_* is used for getting time periods.
These events are combined in user space, then it can be analyzed by
perf tools.

Signed-off-by: Andrew Vagin <avagin@openvz.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arun Sharma <asharma@fb.com>
Link: http://lkml.kernel.org/r/1342088069-1005148-1-git-send-email-avagin@openvz.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-26 12:23:10 +02:00
Ying Xue
014acbf0d5 sched: Fix minor code style issues
Delete redudant spaces between type name and data name or operators.

Signed-off-by: Ying Xue <ying.xue0@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1342076622-6606-1-git-send-email-ying.xue0@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-26 11:47:00 +02:00
Namhyung Kim
45afb1734f sched: Use task_rq_unlock() in __sched_setscheduler()
It seems there's no specific reason to open-code it.  I guess
commit 0122ec5b02 ("sched: Add p->pi_lock to task_rq_lock()")
simply missed it.  Let's be consistent with others.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1341647342-6742-1-git-send-email-namhyung@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-26 11:46:59 +02:00
Peter Zijlstra
8323f26ce3 sched: Fix race in task_group()
Stefan reported a crash on a kernel before a3e5d1091c ("sched:
Don't call task_group() too many times in set_task_rq()"), he
found the reason to be that the multiple task_group()
invocations in set_task_rq() returned different values.

Looking at all that I found a lack of serialization and plain
wrong comments.

The below tries to fix it using an extra pointer which is
updated under the appropriate scheduler locks. Its not pretty,
but I can't really see another way given how all the cgroup
stuff works.

Reported-and-tested-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1340364965.18025.71.camel@twins
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-24 13:58:20 +02:00
Srivatsa Vaddagiri
88b8dac0a1 sched: Improve balance_cpu() to consider other cpus in its group as target of (pinned) task
Current load balance scheme requires only one cpu in a
sched_group (balance_cpu) to look at other peer sched_groups for
imbalance and pull tasks towards itself from a busy cpu. Tasks
thus pulled by balance_cpu could later get picked up by cpus
that are in the same sched_group as that of balance_cpu.

This scheme however fails to pull tasks that are not allowed to
run on balance_cpu (but are allowed to run on other cpus in its
sched_group). That can affect fairness and in some worst case
scenarios cause starvation.

Consider a two core (2 threads/core) system running tasks as
below:

          Core0            Core1
         /     \          /     \
	C0     C1	 C2     C3
        |      |         |      |
        v      v         v      v
	F0     T1        F1     [idle]
			 T2

 F0 = SCHED_FIFO task (pinned to C0)
 F1 = SCHED_FIFO task (pinned to C2)
 T1 = SCHED_OTHER task (pinned to C1)
 T2 = SCHED_OTHER task (pinned to C1 and C2)

F1 could become a cpu hog, which will starve T2 unless C1 pulls
it. Between C0 and C1 however, C0 is required to look for
imbalance between cores, which will fail to pull T2 towards
Core0. T2 will starve eternally in this case. The same scenario
can arise in presence of non-rt tasks as well (say we replace F1
with high irq load).

We tackle this problem by having balance_cpu move pinned tasks
to one of its sibling cpus (where they can run). We first check
if load balance goal can be met by ignoring pinned tasks,
failing which we retry move_tasks() with a new env->dst_cpu.

This patch modifies load balance semantics on who can move load
towards a given cpu in a given sched_domain.

Before this patch, a given_cpu or a ilb_cpu acting on behalf of
an idle given_cpu is responsible for moving load to given_cpu.

With this patch applied, balance_cpu can in addition decide on
moving some load to a given_cpu.

There is a remote possibility that excess load could get moved
as a result of this (balance_cpu and given_cpu/ilb_cpu deciding
*independently* and at *same* time to move some load to a
given_cpu). However we should see less of such conflicting
decisions in practice and moreover subsequent load balance
cycles should correct the excess load moved to given_cpu.

Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Prashanth Nageshappa <prashanth@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4FE06CDB.2060605@linux.vnet.ibm.com
[ minor edits ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-24 13:58:06 +02:00
Prashanth Nageshappa
bbf18b1949 sched: Reset loop counters if all tasks are pinned and we need to redo load balance
While load balancing, if all tasks on the source runqueue are pinned,
we retry after excluding the corresponding source cpu. However, loop counters
env.loop and env.loop_break are not reset before retrying, which can lead
to failure in moving the tasks. In this patch we reset env.loop and
env.loop_break to their inital values before we retry.

Signed-off-by: Prashanth Nageshappa <prashanth@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4FE06EEF.2090709@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-24 13:55:37 +02:00
Prashanth Nageshappa
85c1e7dae1 sched: Reorder 'struct lb_env' members to reduce its size
Members of 'struct lb_env' are not in appropriate order to reuse compiler
added padding on 64bit architectures. In this patch we reorder those struct
members and help reduce the size of the structure from 96 bytes to 80
bytes on 64 bit architectures.

Suggested-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Prashanth Nageshappa <prashanth@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4FE06DDE.7000403@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-24 13:55:20 +02:00
Mike Galbraith
970e178985 sched: Improve scalability via 'CPU buddies', which withstand random perturbations
Traversing an entire package is not only expensive, it also leads to tasks
bouncing all over a partially idle and possible quite large package.  Fix
that up by assigning a 'buddy' CPU to try to motivate.  Each buddy may try
to motivate that one other CPU, if it's busy, tough, it may then try its
SMT sibling, but that's all this optimization is allowed to cost.

Sibling cache buddies are cross-wired to prevent bouncing.

4 socket 40 core + SMT Westmere box, single 30 sec tbench runs, higher is better:

 clients     1       2       4        8       16       32       64      128
 ..........................................................................
 pre        30      41     118      645     3769     6214    12233    14312
 post      299     603    1211     2418     4697     6847    11606    14557

A nice increase in performance.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1339471112.7352.32.camel@marge.simpson.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-24 13:53:34 +02:00
Srivatsa S. Bhat
7ddf96b02f cpusets, hotplug: Restructure functions that are invoked during hotplug
Separate out the cpuset related handling for CPU/Memory online/offline.
This also helps us exploit the most obvious and basic level of optimization
that any notification mechanism (CPU/Mem online/offline) has to offer us:
"We *know* why we have been invoked. So stop pretending that we are lost,
and do only the necessary amount of processing!".

And while at it, rename scan_for_empty_cpusets() to
scan_cpusets_upon_hotplug(), which is more appropriate considering how
it is restructured.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20120524141650.3692.48637.stgit@srivatsabhat.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-24 13:53:22 +02:00
Srivatsa S. Bhat
d35be8bab9 CPU hotplug, cpusets, suspend: Don't modify cpusets during suspend/resume
In the event of CPU hotplug, the kernel modifies the cpusets' cpus_allowed
masks as and when necessary to ensure that the tasks belonging to the cpusets
have some place (online CPUs) to run on. And regular CPU hotplug is
destructive in the sense that the kernel doesn't remember the original cpuset
configurations set by the user, across hotplug operations.

However, suspend/resume (which uses CPU hotplug) is a special case in which
the kernel has the responsibility to restore the system (during resume), to
exactly the same state it was in before suspend.

In order to achieve that, do the following:

1. Don't modify cpusets during suspend/resume. At all.
   In particular, don't move the tasks from one cpuset to another, and
   don't modify any cpuset's cpus_allowed mask. So, simply ignore cpusets
   during the CPU hotplug operations that are carried out in the
   suspend/resume path.

2. However, cpusets and sched domains are related. We just want to avoid
   altering cpusets alone. So, to keep the sched domains updated, build
   a single sched domain (containing all active cpus) during each of the
   CPU hotplug operations carried out in s/r path, effectively ignoring
   the cpusets' cpus_allowed masks.

   (Since userspace is frozen while doing all this, it will go unnoticed.)

3. During the last CPU online operation during resume, build the sched
   domains by looking up the (unaltered) cpusets' cpus_allowed masks.
   That will bring back the system to the same original state as it was in
   before suspend.

Ultimately, this will not only solve the cpuset problem related to suspend
resume (ie., restores the cpusets to exactly what it was before suspend, by
not touching it at all) but also speeds up suspend/resume because we avoid
running cpuset update code for every CPU being offlined/onlined.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20120524141611.3692.20155.stgit@srivatsabhat.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-24 13:53:14 +02:00
Linus Torvalds
ab93eb8216 Merge branches 'core-urgent-for-linus', 'perf-urgent-for-linus' and 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU, perf, and scheduler fixes from Ingo Molnar.

The RCU fix is a revert for an optimization that could cause deadlocks.

One of the scheduler commits (164c33c6ad "sched: Fix fork() error path
to not crash") is correct but not complete (some architectures like Tile
are not covered yet) - the resulting additional fixes are still WIP and
Ingo did not want to delay these pending fixes.  See this thread on
lkml:

  [PATCH] fork: fix error handling in dup_task()

The perf fixes are just trivial oneliners.

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Revert "rcu: Move PREEMPT_RCU preemption to switch_to() invocation"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf kvm: Fix segfault with report and mixed guestmount use
  perf kvm: Fix regression with guest machine creation
  perf script: Fix format regression due to libtraceevent merge
  ring-buffer: Fix accounting of entries when removing pages
  ring-buffer: Fix crash due to uninitialized new_pages list head

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  MAINTAINERS/sched: Update scheduler file pattern
  sched/nohz: Rewrite and fix load-avg computation -- again
  sched: Fix fork() error path to not crash
2012-07-14 11:16:24 -07:00
Peter Zijlstra
5167e8d541 sched/nohz: Rewrite and fix load-avg computation -- again
Thanks to Charles Wang for spotting the defects in the current code:

 - If we go idle during the sample window -- after sampling, we get a
   negative bias because we can negate our own sample.

 - If we wake up during the sample window we get a positive bias
   because we push the sample to a known active period.

So rewrite the entire nohz load-avg muck once again, now adding
copious documentation to the code.

Reported-and-tested-by: Doug Smythies <dsmythies@telus.net>
Reported-and-tested-by: Charles Wang <muming.wq@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/1340373782.18025.74.camel@twins
[ minor edits ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-07-05 20:58:13 +02:00
Paul E. McKenney
cba6d0d64e Revert "rcu: Move PREEMPT_RCU preemption to switch_to() invocation"
This reverts commit 616c310e83.
(Move PREEMPT_RCU preemption to switch_to() invocation).
Testing by Sasha Levin <levinsasha928@gmail.com> showed that this
can result in deadlock due to invoking the scheduler when one of
the runqueue locks is held.  Because this commit was simply a
performance optimization, revert it.

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Sasha Levin <levinsasha928@gmail.com>
2012-07-02 11:39:19 -07:00
Linus Torvalds
7249450449 Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar.

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Fix the relax_domain_level boot parameter
  sched: Validate assumptions in sched_init_numa()
  sched: Always initialize cpu-power
  sched: Fix domain iteration
  sched/rt: Fix lockdep annotation within find_lock_lowest_rq()
  sched/numa: Load balance between remote nodes
  sched/x86: Calculate booted cores after construction of sibling_mask
2012-06-08 14:59:29 -07:00
Randy Dunlap
cd96891d48 sched/fair: fix lots of kernel-doc warnings
Fix lots of new kernel-doc warnings in kernel/sched/fair.c:

  Warning(kernel/sched/fair.c:3625): No description found for parameter 'env'
  Warning(kernel/sched/fair.c:3625): Excess function parameter 'sd' description in 'update_sg_lb_stats'
  Warning(kernel/sched/fair.c:3735): No description found for parameter 'env'
  Warning(kernel/sched/fair.c:3735): Excess function parameter 'sd' description in 'update_sd_pick_busiest'
  Warning(kernel/sched/fair.c:3735): Excess function parameter 'this_cpu' description in 'update_sd_pick_busiest'
  .. more warnings

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-08 14:59:10 -07:00
Dimitri Sivanich
a841f8cef4 sched: Fix the relax_domain_level boot parameter
It does not get processed because sched_domain_level_max is 0 at the
time that setup_relax_domain_level() is run.

Simply accept the value as it is, as we don't know the value of
sched_domain_level_max until sched domain construction is completed.

Fix sched_relax_domain_level in cpuset.  The build_sched_domain() routine calls
the set_domain_attribute() routine prior to setting the sd->level, however,
the set_domain_attribute() routine relies on the sd->level to decide whether
idle load balancing will be off/on.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120605184436.GA15668@sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-06-06 17:07:41 +02:00
Peter Zijlstra
d039ac6080 sched: Validate assumptions in sched_init_numa()
Add some code to validate assumptions we're making and output
warnings if they are not.

If this trigger we want to know about it.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alex Shi <lkml.alex@gmail.com>
Link: http://lkml.kernel.org/n/tip-6uc3wk5s9udxtdl9cnku0vtt@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-06-06 16:52:30 +02:00
Peter Zijlstra
c3decf0dfb sched: Always initialize cpu-power
Often when we run into mis-shapen topologies the balance iteration
fails to update the cpu power properly and we'll end up in /0 traps.

Always initialize the cpu-power to a semi-sane value so that we can
at least boot the machine, even if the load-balancer might not
function correctly.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-3lbhyj25sr169ha7z3qht5na@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-06-06 16:52:27 +02:00
Peter Zijlstra
c117487687 sched: Fix domain iteration
Weird topologies can lead to asymmetric domain setups. This needs
further consideration since these setups are typically non-minimal
too.

For now, make it work by adding an extra mask selecting which CPUs
are allowed to iterate up.

The topology that triggered it is the one from David Rientjes:

	10 20 20 30
	20 10 20 20
	20 20 10 20
	30 20 20 10

resulting in boxes that wouldn't even boot.

Reported-by: David Rientjes <rientjes@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-3p86l9cuaqnxz7uxsojmz5rm@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-06-06 16:52:26 +02:00
Peter Zijlstra
7f1b43936f sched/rt: Fix lockdep annotation within find_lock_lowest_rq()
Roland Dreier reported spurious, hard to trigger lockdep warnings
within the scheduler - without any real lockup.

This bit gives us the right clue:

> [89945.640512]  [<ffffffff8103fa1a>] double_lock_balance+0x5a/0x90
> [89945.640568]  [<ffffffff8104c546>] push_rt_task+0xc6/0x290

if you look at that code you'll find the double_lock_balance() in
question is the one in find_lock_lowest_rq() [yay for inlining].

Now find_lock_lowest_rq() has a bug.. it fails to use
double_unlock_balance() in one exit path, if this results in a retry in
push_rt_task() we'll call double_lock_balance() again, at which point
we'll run into said lockdep confusion.

Reported-by: Roland Dreier <roland@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1337282386.4281.77.camel@twins
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-06-06 16:52:26 +02:00
Alex Shi
10717dcde1 sched/numa: Load balance between remote nodes
Commit cb83b629b ("sched/numa: Rewrite the CONFIG_NUMA sched
domain support") removed the NODE sched domain and started checking
if the node distance in SLIT table is farther than REMOTE_DISTANCE,
if so, it will lose the load balance chance at exec/fork/wake_affine
points.

But actually, even the node distance is farther than REMOTE_DISTANCE.

Modern CPUs also has QPI like connections, which ensures that memory
access is not too slow between nodes. So the above change in behavior
on NUMA machine causes a performance regression on various benchmarks:
hackbench, tbench, netperf, oltp, etc.

This patch will recover the scheduler behavior to old mode on all my
Intel platforms: NHM EP/EX, WSM EP, SNB EP/EP4S, and thus fixes the
perfromance regressions. (all of them just have 2 kinds distance, 10, 21)

Signed-off-by: Alex Shi <alex.shi@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1338965571-9812-1-git-send-email-alex.shi@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-06-06 16:52:25 +02:00
Kamalesh Babulal
6a4c96eef4 sched: Remove NULL assignment of dattr_cur
Remove explicit NULL assignment of static pointer
dattr_cur from init_sched_domains().

Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120523091411.GG5005@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-30 14:02:27 +02:00
Hiroshi Shimamoto
7997a456ef sched: Remove the last NULL entry from sched_feat_names
No need to have the last NULL entry.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4FBF29E7.5020805@ct.jp.nec.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-30 14:02:27 +02:00
Hiroshi Shimamoto
1292531f6f sched: Make sched_feat_names const
The strings sched_feat_names are never changed.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4FBF29B2.9030904@ct.jp.nec.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-30 14:02:26 +02:00
Colin Cross
454c79999f sched/rt: Fix SCHED_RR across cgroups
task_tick_rt() has an optimization to only reschedule SCHED_RR tasks
if they were the only element on their rq.  However, with cgroups
a SCHED_RR task could be the only element on its per-cgroup rq but
still be competing with other SCHED_RR tasks in its parent's
cgroup.  In this case, the SCHED_RR task in the child cgroup would
never yield at the end of its timeslice.  If the child cgroup
rt_runtime_us was the same as the parent cgroup rt_runtime_us,
the task in the parent cgroup would starve completely.

Modify task_tick_rt() to check that the task is the only task on its
rq, and that the each of the scheduling entities of its ancestors
is also the only entity on its rq.

Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1337229266-15798-1-git-send-email-ccross@android.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-30 14:02:25 +02:00
Peter Zijlstra
29baa7478b sched: Move nr_cpus_allowed out of 'struct sched_rt_entity'
Since nr_cpus_allowed is used outside of sched/rt.c and wants to be
used outside of there more, move it to a more natural site.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-kr61f02y9brwzkh6x53pdptm@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-30 14:02:25 +02:00
Peter Zijlstra
b654f7de41 sched: Make sure to not re-read variables after validation
We could re-read rq->rt_avg after we validated it was smaller than
total, invalidating the check and resulting in an unintended negative.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: David Rientjes <rientjes@google.com>
Link: http://lkml.kernel.org/r/1337688268.9698.29.camel@twins
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-30 14:02:24 +02:00
Peter Zijlstra
74a5ce20e6 sched: Fix SD_OVERLAP
SD_OVERLAP exists to allow overlapping groups, overlapping groups
appear in NUMA topologies that aren't fully connected.

The typical result of not fully connected NUMA is that each cpu (or
rather node) will have different spans for a particular distance.
However due to how sched domains are traversed -- only the first cpu
in the mask goes one level up -- the next level only cares about the
spans of the cpus that went up.

Due to this two things were observed to be broken:

 - build_overlap_sched_groups() -- since its possible the cpu we're
   building the groups for exists in multiple (or all) groups, the
   selection criteria of the first group didn't ensure there was a cpu
   for which is was true that cpumask_first(span) == cpu. Thus load-
   balancing would terminate.

 - update_group_power() -- assumed that the cpu span of the first
   group of the domain was covered by all groups of the child domain.
   The above explains why this isn't true, so deal with it.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: David Rientjes <rientjes@google.com>
Link: http://lkml.kernel.org/r/1337788843.9783.14.camel@laptop
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-30 14:02:24 +02:00
Peter Zijlstra
2ea45800d8 sched: Don't try allocating memory from offline nodes
Allocators don't appreciate it when you try and allocate memory from
offline nodes.

Reported-and-tested-by: Tony Luck <tony.luck@intel.com>
Reported-and-tested-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-epfc1io9whb7o22bcujf31vn@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-30 14:02:23 +02:00
Peter Zijlstra
5aaa0b7a2e sched/nohz: Fix rq->cpu_load calculations some more
Follow up on commit 556061b00 ("sched/nohz: Fix rq->cpu_load[]
calculations") since while that fixed the busy case it regressed the
mostly idle case.

Add a callback from the nohz exit to also age the rq->cpu_load[]
array. This closes the hole where either there was no nohz load
balance pass during the nohz, or there was a 'significant' amount of
idle time between the last nohz balance and the nohz exit.

So we'll update unconditionally from the tick to not insert any
accidental 0 load periods while busy, and we try and catch up from
nohz idle balance and nohz exit. Both these are still prone to missing
a jiffy, but that has always been the case.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: pjt@google.com
Cc: Venkatesh Pallipadi <venki@google.com>
Link: http://lkml.kernel.org/n/tip-kt0trz0apodbf84ucjfdbr1a@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-30 14:02:16 +02:00
Linus Torvalds
644473e9c6 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull user namespace enhancements from Eric Biederman:
 "This is a course correction for the user namespace, so that we can
  reach an inexpensive, maintainable, and reasonably complete
  implementation.

  Highlights:
   - Config guards make it impossible to enable the user namespace and
     code that has not been converted to be user namespace safe.

   - Use of the new kuid_t type ensures the if you somehow get past the
     config guards the kernel will encounter type errors if you enable
     user namespaces and attempt to compile in code whose permission
     checks have not been updated to be user namespace safe.

   - All uids from child user namespaces are mapped into the initial
     user namespace before they are processed.  Removing the need to add
     an additional check to see if the user namespace of the compared
     uids remains the same.

   - With the user namespaces compiled out the performance is as good or
     better than it is today.

   - For most operations absolutely nothing changes performance or
     operationally with the user namespace enabled.

   - The worst case performance I could come up with was timing 1
     billion cache cold stat operations with the user namespace code
     enabled.  This went from 156s to 164s on my laptop (or 156ns to
     164ns per stat operation).

   - (uid_t)-1 and (gid_t)-1 are reserved as an internal error value.
     Most uid/gid setting system calls treat these value specially
     anyway so attempting to use -1 as a uid would likely cause
     entertaining failures in userspace.

   - If setuid is called with a uid that can not be mapped setuid fails.
     I have looked at sendmail, login, ssh and every other program I
     could think of that would call setuid and they all check for and
     handle the case where setuid fails.

   - If stat or a similar system call is called from a context in which
     we can not map a uid we lie and return overflowuid.  The LFS
     experience suggests not lying and returning an error code might be
     better, but the historical precedent with uids is different and I
     can not think of anything that would break by lying about a uid we
     can't map.

   - Capabilities are localized to the current user namespace making it
     safe to give the initial user in a user namespace all capabilities.

  My git tree covers all of the modifications needed to convert the core
  kernel and enough changes to make a system bootable to runlevel 1."

Fix up trivial conflicts due to nearby independent changes in fs/stat.c

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (46 commits)
  userns:  Silence silly gcc warning.
  cred: use correct cred accessor with regards to rcu read lock
  userns: Convert the move_pages, and migrate_pages permission checks to use uid_eq
  userns: Convert cgroup permission checks to use uid_eq
  userns: Convert tmpfs to use kuid and kgid where appropriate
  userns: Convert sysfs to use kgid/kuid where appropriate
  userns: Convert sysctl permission checks to use kuid and kgids.
  userns: Convert proc to use kuid/kgid where appropriate
  userns: Convert ext4 to user kuid/kgid where appropriate
  userns: Convert ext3 to use kuid/kgid where appropriate
  userns: Convert ext2 to use kuid/kgid where appropriate.
  userns: Convert devpts to use kuid/kgid where appropriate
  userns: Convert binary formats to use kuid/kgid where appropriate
  userns: Add negative depends on entries to avoid building code that is userns unsafe
  userns: signal remove unnecessary map_cred_ns
  userns: Teach inode_capable to understand inodes whose uids map to other namespaces.
  userns: Fail exec for suid and sgid binaries with ids outside our user namespace.
  userns: Convert stat to return values mapped from kuids and kgids
  userns: Convert user specfied uids and gids in chown into kuids and kgid
  userns: Use uid_eq gid_eq helpers when comparing kuids and kgids in the vfs
  ...
2012-05-23 17:42:39 -07:00
Linus Torvalds
56edab3159 Merge branches 'perf-urgent-for-linus' and 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Ingo Molnar:

 - Leftover AMD PMU driver fix fix from the end of the v3.4
   stabilization cycle.

 - Late tools/perf/ changes that missed the first round:
    * endianness fixes
    * event parsing improvements
    * libtraceevent fixes factored out from trace-cmd
    * perl scripting engine fixes related to libtraceevent,
    * testcase improvements
    * perf inject / pipe mode fixes
    * plus a kernel side fix

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86: Update event scheduling constraints for AMD family 15h models

* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Revert "sched, perf: Use a single callback into the scheduler"
  perf evlist: Show event attribute details
  perf tools: Bump default sample freq to 4 kHz
  perf buildid-list: Work better with pipe mode
  perf tools: Fix piped mode read code
  perf inject: Fix broken perf inject -b
  perf tools: rename HEADER_TRACE_INFO to HEADER_TRACING_DATA
  perf tools: Add union u64_swap type for swapping u64 data
  perf tools: Carry perf_event_attr bitfield throught different endians
  perf record: Fix documentation for branch stack sampling
  perf target: Add cpu flag to sample_type if target has cpu
  perf tools: Always try to build libtraceevent
  perf tools: Rename libparsevent to libtraceevent in Makefile
  perf script: Rename struct event to struct event_format in perl engine
  perf script: Explicitly handle known default print arg type
  perf tools: Add hardcoded name term for pmu events
  perf tools: Separate 'mem:' event scanner bits
  perf tools: Use allocated list for each parsed event
  perf tools: Add support for displaying event parser debug info
  perf test: Move parse event automated tests to separated object
2012-05-23 12:12:49 -07:00
Jiri Olsa
ab0cce560e Revert "sched, perf: Use a single callback into the scheduler"
This reverts commit cb04ff9ac4 ("sched, perf: Use a single
callback into the scheduler").

Before this change was introduced, the process switch worked
like this (wrt. to perf event schedule):

     schedule (prev, next)
       - schedule out all perf events for prev
       - switch to next
       - schedule in all perf events for current (next)

After the commit, the process switch looks like:

     schedule (prev, next)
       - schedule out all perf events for prev
       - schedule in all perf events for (next)
       - switch to next

The problem is, that after we schedule perf events in, the pmu
is enabled and we can receive events even before we make the
switch to next - so "current" still being prev process (event
SAMPLE data are filled based on the value of the "current"
process).

Thats exactly what we see for test__PERF_RECORD test. We receive
SAMPLES with PID of the process that our tracee is scheduled
from.

Discussed with Peter Zijlstra:

 > Bah!, yeah I guess reverting is the right thing for now. Sad
 > though.
 >
 > So by having the two hooks we have a black-spot between them
 > where we receive no events at all, this black-spot covers the
 > hand-over of current and we thus don't receive the 'wrong'
 > events.
 >
 > I rather liked we could do away with both that black-spot and
 > clean up the code a little, but apparently people rely on it.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: acme@redhat.com
Cc: paulus@samba.org
Cc: cjashfor@linux.vnet.ibm.com
Cc: fweisbec@gmail.com
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/20120523111302.GC1638@m.brq.redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-23 17:40:51 +02:00
Linus Torvalds
d79ee93de9 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler changes from Ingo Molnar:
 "The biggest change is the cleanup/simplification of the load-balancer:
  instead of the current practice of architectures twiddling scheduler
  internal data structures and providing the scheduler domains in
  colorfully inconsistent ways, we now have generic scheduler code in
  kernel/sched/core.c:sched_init_numa() that looks at the architecture's
  node_distance() parameters and (while not fully trusting it) deducts a
  NUMA topology from it.

  This inevitably changes balancing behavior - hopefully for the better.

  There are various smaller optimizations, cleanups and fixlets as well"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Taint kernel with TAINT_WARN after sleep-in-atomic bug
  sched: Remove stale power aware scheduling remnants and dysfunctional knobs
  sched/debug: Fix printing large integers on 32-bit platforms
  sched/fair: Improve the ->group_imb logic
  sched/nohz: Fix rq->cpu_load[] calculations
  sched/numa: Don't scale the imbalance
  sched/fair: Revert sched-domain iteration breakage
  sched/x86: Rewrite set_cpu_sibling_map()
  sched/numa: Fix the new NUMA topology bits
  sched/numa: Rewrite the CONFIG_NUMA sched domain support
  sched/fair: Propagate 'struct lb_env' usage into find_busiest_group
  sched/fair: Add some serialization to the sched_domain load-balance walk
  sched/fair: Let minimally loaded cpu balance the group
  sched: Change rq->nr_running to unsigned int
  x86/numa: Check for nonsensical topologies on real hw as well
  x86/numa: Hard partition cpu topology masks on node boundaries
  x86/numa: Allow specifying node_distance() for numa=fake
  x86/sched: Make mwait_usable() heed to "idle=" kernel parameters properly
  sched: Update documentation and comments
  sched_rt: Avoid unnecessary dequeue and enqueue of pushable tasks in set_cpus_allowed_rt()
2012-05-22 18:27:32 -07:00
Linus Torvalds
2ff2b289a6 Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf changes from Ingo Molnar:
 "Lots of changes:

   - (much) improved assembly annotation support in perf report, with
     jump visualization, searching, navigation, visual output
     improvements and more.

    - kernel support for AMD IBS PMU hardware features.  Notably 'perf
      record -e cycles:p' and 'perf top -e cycles:p' should work without
      skid now, like PEBS does on the Intel side, because it takes
      advantage of IBS transparently.

    - the libtracevents library: it is the first step towards unifying
      tracing tooling and perf, and it also gives a tracing library for
      external tools like powertop to rely on.

    - infrastructure: various improvements and refactoring of the UI
      modules and related code

    - infrastructure: cleanup and simplification of the profiling
      targets code (--uid, --pid, --tid, --cpu, --all-cpus, etc.)

    - tons of robustness fixes all around

    - various ftrace updates: speedups, cleanups, robustness
      improvements.

    - typing 'make' in tools/ will now give you a menu of projects to
      build and a short help text to explain what each does.

    - ... and lots of other changes I forgot to list.

  The perf record make bzImage + perf report regression you reported
  should be fixed."

* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (166 commits)
  tracing: Remove kernel_lock annotations
  tracing: Fix initial buffer_size_kb state
  ring-buffer: Merge separate resize loops
  perf evsel: Create events initially disabled -- again
  perf tools: Split term type into value type and term type
  perf hists: Fix callchain ip printf format
  perf target: Add uses_mmap field
  ftrace: Remove selecting FRAME_POINTER with FUNCTION_TRACER
  ftrace/x86: Have x86 ftrace use the ftrace_modify_all_code()
  ftrace: Make ftrace_modify_all_code() global for archs to use
  ftrace: Return record ip addr for ftrace_location()
  ftrace: Consolidate ftrace_location() and ftrace_text_reserved()
  ftrace: Speed up search by skipping pages by address
  ftrace: Remove extra helper functions
  ftrace: Sort all function addresses, not just per page
  tracing: change CPU ring buffer state from tracing_cpumask
  tracing: Check return value of tracing_dentry_percpu()
  ring-buffer: Reset head page before running self test
  ring-buffer: Add integrity check at end of iter read
  ring-buffer: Make addition of pages in ring buffer atomic
  ...
2012-05-22 18:18:55 -07:00
Linus Torvalds
88d6ae8dc3 Merge branch 'for-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
 "cgroup file type addition / removal is updated so that file types are
  added and removed instead of individual files so that dynamic file
  type addition / removal can be implemented by cgroup and used by
  controllers.  blkio controller changes which will come through block
  tree are dependent on this.  Other changes include res_counter cleanup
  and disallowing kthread / PF_THREAD_BOUND threads to be attached to
  non-root cgroups.

  There's a reported bug with the file type addition / removal handling
  which can lead to oops on cgroup umount.  The issue is being looked
  into.  It shouldn't cause problems for most setups and isn't a
  security concern."

Fix up trivial conflict in Documentation/feature-removal-schedule.txt

* 'for-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits)
  res_counter: Account max_usage when calling res_counter_charge_nofail()
  res_counter: Merge res_counter_charge and res_counter_charge_nofail
  cgroups: disallow attaching kthreadd or PF_THREAD_BOUND threads
  cgroup: remove cgroup_subsys->populate()
  cgroup: get rid of populate for memcg
  cgroup: pass struct mem_cgroup instead of struct cgroup to socket memcg
  cgroup: make css->refcnt clearing on cgroup removal optional
  cgroup: use negative bias on css->refcnt to block css_tryget()
  cgroup: implement cgroup_rm_cftypes()
  cgroup: introduce struct cfent
  cgroup: relocate __d_cgrp() and __d_cft()
  cgroup: remove cgroup_add_file[s]()
  cgroup: convert memcg controller to the new cftype interface
  memcg: always create memsw files if CONFIG_CGROUP_MEM_RES_CTLR_SWAP
  cgroup: convert all non-memcg controllers to the new cftype interface
  cgroup: relocate cftype and cgroup_subsys definitions in controllers
  cgroup: merge cft_release_agent cftype array into the base files array
  cgroup: implement cgroup_add_cftypes() and friends
  cgroup: build list of all cgroups under a given cgroupfs_root
  cgroup: move cgroup_clear_directory() call out of cgroup_populate_dir()
  ...
2012-05-22 17:40:19 -07:00
Linus Torvalds
bf67f3a5c4 Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull smp hotplug cleanups from Thomas Gleixner:
 "This series is merily a cleanup of code copied around in arch/* and
  not changing any of the real cpu hotplug horrors yet.  I wish I'd had
  something more substantial for 3.5, but I underestimated the lurking
  horror..."

Fix up trivial conflicts in arch/{arm,sparc,x86}/Kconfig and
arch/sparc/include/asm/thread_info_32.h

* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (79 commits)
  um: Remove leftover declaration of alloc_task_struct_node()
  task_allocator: Use config switches instead of magic defines
  sparc: Use common threadinfo allocator
  score: Use common threadinfo allocator
  sh-use-common-threadinfo-allocator
  mn10300: Use common threadinfo allocator
  powerpc: Use common threadinfo allocator
  mips: Use common threadinfo allocator
  hexagon: Use common threadinfo allocator
  m32r: Use common threadinfo allocator
  frv: Use common threadinfo allocator
  cris: Use common threadinfo allocator
  x86: Use common threadinfo allocator
  c6x: Use common threadinfo allocator
  fork: Provide kmemcache based thread_info allocator
  tile: Use common threadinfo allocator
  fork: Provide weak arch_release_[task_struct|thread_info] functions
  fork: Move thread info gfp flags to header
  fork: Remove the weak insanity
  sh: Remove cpu_idle_wait()
  ...
2012-05-21 19:43:57 -07:00
Linus Torvalds
226da0dbc8 Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU changes from Ingo Molnar:
 "This is the v3.5 RCU tree from Paul E.  McKenney:

 1) A set of improvements and fixes to the RCU_FAST_NO_HZ feature (with
    more on the way for 3.6).  Posted to LKML:
       https://lkml.org/lkml/2012/4/23/324 (commits 1-3 and 5),
       https://lkml.org/lkml/2012/4/16/611 (commit 4),
       https://lkml.org/lkml/2012/4/30/390 (commit 6), and
       https://lkml.org/lkml/2012/5/4/410 (commit 7, combined with
       the other commits for the convenience of the tester).

 2) Changes to make rcu_barrier() avoid disrupting execution of CPUs
    that have no RCU callbacks.  Posted to LKML:
       https://lkml.org/lkml/2012/4/23/322.

 3) A couple of commits that improve the efficiency of the interaction
    between preemptible RCU and the scheduler, these two being all that
    survived an abortive attempt to allow preemptible RCU's
    __rcu_read_lock() to be inlined.  The full set was posted to LKML at
    https://lkml.org/lkml/2012/4/14/143, and the first and third patches
    of that set remain.

 4) Lai Jiangshan's algorithmic implementation of SRCU, which includes
    call_srcu() and srcu_barrier().  A major feature of this new
    implementation is that synchronize_srcu() no longer disturbs the
    execution of other CPUs.  This work is based on earlier
    implementations by Peter Zijlstra and Paul E.  McKenney.  Posted to
    LKML: https://lkml.org/lkml/2012/2/22/82.

 5) A number of miscellaneous bug fixes and improvements which were
    posted to LKML at: https://lkml.org/lkml/2012/4/23/353 with
    subsequent updates posted to LKML."

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (32 commits)
  rcu: Make rcu_barrier() less disruptive
  rcu: Explicitly initialize RCU_FAST_NO_HZ per-CPU variables
  rcu: Make RCU_FAST_NO_HZ handle timer migration
  rcu: Update RCU maintainership
  rcu: Make exit_rcu() more precise and consolidate
  rcu: Move PREEMPT_RCU preemption to switch_to() invocation
  rcu: Ensure that RCU_FAST_NO_HZ timers expire on correct CPU
  rcu: Add rcutorture test for call_srcu()
  rcu: Implement per-domain single-threaded call_srcu() state machine
  rcu: Use single value to handle expedited SRCU grace periods
  rcu: Improve srcu_readers_active_idx()'s cache locality
  rcu: Remove unused srcu_barrier()
  rcu: Implement a variant of Peter's SRCU algorithm
  rcu: Improve SRCU's wait_idx() comments
  rcu: Flip ->completed only once per SRCU grace period
  rcu: Increment upper bit only for srcu_read_lock()
  rcu: Remove fast check path from __synchronize_srcu()
  rcu: Direct algorithmic SRCU implementation
  rcu: Introduce rcutorture testing for rcu_barrier()
  timer: Fix mod_timer_pinned() header comment
  ...
2012-05-21 19:26:51 -07:00
Arnaldo Carvalho de Melo
16ee6576e2 Merge remote-tracking branch 'tip/perf/urgent' into perf/core
Merge reason: We are going to queue up a dependent patch:

"perf tools: Move parse event automated tests to separated object"

That depends on:

commit e7c72d8
perf tools: Add 'G' and 'H' modifiers to event parsing

Conflicts:
	tools/perf/builtin-stat.c

Conflicted with the recent 'perf_target' patches when checking the
result of perf_evsel open routines to see if a retry is needed to cope
with older kernels where the exclude guest/host perf_event_attr bits
were not used.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2012-05-18 13:13:33 -03:00
Konstantin Khlebnikov
1c2927f185 sched: Taint kernel with TAINT_WARN after sleep-in-atomic bug
Usually sleep-in-atomic bugs are followed by dozens other warnings.
This patch should help to figure out original source of problem.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120510122004.4873.12726.stgit@zurg
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-18 13:07:40 +02:00
Peter Zijlstra
8e7fbcbc22 sched: Remove stale power aware scheduling remnants and dysfunctional knobs
It's been broken forever (i.e. it's not scheduling in a power
aware fashion), as reported by Suresh and others sending
patches, and nobody cares enough to fix it properly ...
so remove it to make space free for something better.

There's various problems with the code as it stands today, first
and foremost the user interface which is bound to topology
levels and has multiple values per level. This results in a
state explosion which the administrator or distro needs to
master and almost nobody does.

Furthermore large configuration state spaces aren't good, it
means the thing doesn't just work right because it's either
under so many impossibe to meet constraints, or even if
there's an achievable state workloads have to be aware of
it precisely and can never meet it for dynamic workloads.

So pushing this kind of decision to user-space was a bad idea
even with a single knob - it's exponentially worse with knobs
on every node of the topology.

There is a proposal to replace the user interface with a single
3 state knob:

 sched_balance_policy := { performance, power, auto }

where 'auto' would be the preferred default which looks at things
like Battery/AC mode and possible cpufreq state or whatever the hw
exposes to show us power use expectations - but there's been no
progress on it in the past many months.

Aside from that, the actual implementation of the various knobs
is known to be broken. There have been sporadic attempts at
fixing things but these always stop short of reaching a mergable
state.

Therefore this wholesale removal with the hopes of spurring
people who care to come forward once again and work on a
coherent replacement.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1326104915.2442.53.camel@twins
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-17 13:48:56 +02:00
Ingo Molnar
fac536f7e4 Merge branch 'sched/urgent' into sched/core
Merge reason: bring together all the pending scheduler bits,
              for the sched/numa changes.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-17 12:17:12 +02:00
Peter Zijlstra
13e099d2f7 sched/debug: Fix printing large integers on 32-bit platforms
Some numbers like nr_running and nr_uninterruptible are fundamentally
unsigned since its impossible to have a negative amount of tasks, yet
we still print them as signed to easily recognise the underflow
condition.

rq->nr_uninterruptible has 'special' accounting and can in fact very
easily become negative on a per-cpu basis.

It was noted that since the P() macro assumes things are long long and
the promotion of unsigned 'int/long' to long long on 32bit doesn't
sign extend we print silly large numbers instead of the easier to read
signed numbers.

Therefore extend the P() macro to not require the sign extention.

Reported-by: Diwakar Tundlam <dtundlam@nvidia.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-gk5tm8t2n4ix2vkpns42uqqp@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-14 15:05:28 +02:00
Peter Zijlstra
e44bc5c5d0 sched/fair: Improve the ->group_imb logic
Group imbalance is meant to deal with situations where affinity masks
and sched domains don't align well, such as 3 cpus from one group and
6 from another. In this case the domain based balancer will want to
put an equal amount of tasks on each side even though they don't have
equal cpus.

Currently group_imb is set whenever two cpus of a group have a weight
difference of at least one avg task and the heaviest cpu has at least
two tasks. A group with imbalance set will always be picked as busiest
and a balance pass will be forced.

The problem is that even if there are no affinity masks this stuff can
trigger and cause weird balancing decisions, eg. the observed
behaviour was that of 6 cpus, 5 had 2 and 1 had 3 tasks, due to the
difference of 1 avg load (they all had the same weight) and nr_running
being >1 the group_imbalance logic triggered and did the weird thing
of pulling more load instead of trying to move the 1 excess task to
the other domain of 6 cpus that had 5 cpu with 2 tasks and 1 cpu with
1 task.

Curb the group_imbalance stuff by making the nr_running condition
weaker by also tracking the min_nr_running and using the difference in
nr_running over the set instead of the absolute max nr_running.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-9s7dedozxo8kjsb9kqlrukkf@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-14 15:05:28 +02:00
Peter Zijlstra
556061b00c sched/nohz: Fix rq->cpu_load[] calculations
While investigating why the load-balancer did funny I found that the
rq->cpu_load[] tables were completely screwy.. a bit more digging
revealed that the updates that got through were missing ticks followed
by a catchup of 2 ticks.

The catchup assumes the cpu was idle during that time (since only nohz
can cause missed ticks and the machine is idle etc..) this means that
esp. the higher indices were significantly lower than they ought to
be.

The reason for this is that its not correct to compare against jiffies
on every jiffy on any other cpu than the cpu that updates jiffies.

This patch cludges around it by only doing the catch-up stuff from
nohz_idle_balance() and doing the regular stuff unconditionally from
the tick.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: pjt@google.com
Cc: Venkatesh Pallipadi <venki@google.com>
Link: http://lkml.kernel.org/n/tip-tp4kj18xdd5aj4vvj0qg55s2@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-14 15:05:27 +02:00
Peter Zijlstra
870a0bb5d6 sched/numa: Don't scale the imbalance
It's far too easy to get ridiculously large imbalance pct when you
scale it like that. Use a fixed 125% for now.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-zsriaft1dv7hhboyrpvqjy6s@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-14 15:05:26 +02:00
Peter Zijlstra
04f733b4af sched/fair: Revert sched-domain iteration breakage
Patches c22402a2f ("sched/fair: Let minimally loaded cpu balance the
group") and 0ce90475 ("sched/fair: Add some serialization to the
sched_domain load-balance walk") are horribly broken so revert them.

The problem is that while it sounds good to have the minimally loaded
cpu do the pulling of more load, the way we walk the domains there is
absolutely no guarantee this cpu will actually get to the domain. In
fact its very likely it wont. Therefore the higher up the tree we get,
the less likely it is we'll balance at all.

The first of mask always walks up, while sucky in that it accumulates
load on the first cpu and needs extra passes to spread it out at least
guarantees a cpu gets up that far and load-balancing happens at all.

Since its now always the first and idle cpus should always be able to
balance so they get a task as fast as possible we can also do away
with the added serialization.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-rpuhs5s56aiv1aw7khv9zkw6@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-14 15:05:26 +02:00
Peter Zijlstra
dd7d8634e6 sched/numa: Fix the new NUMA topology bits
There's no need to convert a node number to a node number by
pretending its a cpu number..

Reported-by: Yinghai Lu <yinghai@kernel.org>
Reported-and-Tested-by: Greg Pearson <greg.pearson@hp.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-0sqhrht34phowgclj12dgk8h@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-14 15:05:25 +02:00
Ingo Molnar
2d84e023cb Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull the v3.5 RCU tree from Paul E. McKenney:

 1)	A set of improvements and fixes to the RCU_FAST_NO_HZ feature
	(with more on the way for 3.6).  Posted to LKML:
	https://lkml.org/lkml/2012/4/23/324 (commits 1-3 and 5),
	https://lkml.org/lkml/2012/4/16/611 (commit 4),
	https://lkml.org/lkml/2012/4/30/390 (commit 6), and
	https://lkml.org/lkml/2012/5/4/410 (commit 7, combined with
	the other commits for the convenience of the tester).

 2)	Changes to make rcu_barrier() avoid disrupting execution of CPUs
	that have no RCU callbacks.  Posted to LKML:
	https://lkml.org/lkml/2012/4/23/322.

 3)	A couple of commits that improve the efficiency of the interaction
	between preemptible RCU and the scheduler, these two being all
	that survived an abortive attempt to allow preemptible RCU's
	__rcu_read_lock() to be inlined.  The full set was posted to
	LKML at https://lkml.org/lkml/2012/4/14/143, and the first and
	third patches of that set remain.

 4)	Lai Jiangshan's algorithmic implementation of SRCU, which includes
	call_srcu() and srcu_barrier().  A major feature of this new
	implementation is that synchronize_srcu() no longer disturbs
	the execution of other CPUs.  This work is based on earlier
	implementations by Peter Zijlstra and Paul E. McKenney.  Posted to
	LKML: https://lkml.org/lkml/2012/2/22/82.

 5)	A number of miscellaneous bug fixes and improvements which were
	posted to LKML at: https://lkml.org/lkml/2012/4/23/353 with
	subsequent updates posted to LKML.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-14 08:41:46 +02:00
Peter Zijlstra
cb04ff9ac4 sched, perf: Use a single callback into the scheduler
We can easily use a single callback for both sched-in and sched-out. This
reduces the code footprint in the scheduler path as well as removes
the PMU black spot otherwise present between the out and in callback.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-o56ajxp1edwqg6x9d31wb805@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-09 15:23:17 +02:00
Peter Zijlstra
cb83b629ba sched/numa: Rewrite the CONFIG_NUMA sched domain support
The current code groups up to 16 nodes in a level and then puts an
ALLNODES domain spanning the entire tree on top of that. This doesn't
reflect the numa topology and esp for the smaller not-fully-connected
machines out there today this might make a difference.

Therefore, build a proper numa topology based on node_distance().

Since there's no fixed numa layers anymore, the static SD_NODE_INIT
and SD_ALLNODES_INIT aren't usable anymore, the new code tries to
construct something similar and scales some values either on the
number of cpus in the domain and/or the node_distance() ratio.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Anton Blanchard <anton@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: linux-alpha@vger.kernel.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-sh@vger.kernel.org
Cc: Matt Turner <mattst88@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: sparclinux@vger.kernel.org
Cc: Tony Luck <tony.luck@intel.com>
Cc: x86@kernel.org
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Greg Pearson <greg.pearson@hp.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: bob.picco@oracle.com
Cc: chris.mason@oracle.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-r74n3n8hhuc2ynbrnp3vt954@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-09 15:00:55 +02:00
Peter Zijlstra
bd939f45da sched/fair: Propagate 'struct lb_env' usage into find_busiest_group
More function argument passing reduction.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-v66ivjfqdiqdso01lqgqx6qf@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-09 15:00:54 +02:00
Peter Zijlstra
0ce90475dc sched/fair: Add some serialization to the sched_domain load-balance walk
Since the sched_domain walk is completely unserialized (!SD_SERIALIZE)
it is possible that multiple cpus in the group get elected to do the
next level. Avoid this by adding some serialization.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-vqh9ai6s0ewmeakjz80w4qz6@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-09 15:00:53 +02:00
Peter Zijlstra
c22402a2f7 sched/fair: Let minimally loaded cpu balance the group
Currently we let the leftmost (or first idle) cpu ascend the
sched_domain tree and perform load-balancing. The result is that the
busiest cpu in the group might be performing this function and pull
more load to itself. The next load balance pass will then try to
equalize this again.

Change this to pick the least loaded cpu to perform higher domain
balancing.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-v8zlrmgmkne3bkcy9dej1fvm@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-09 15:00:51 +02:00
Peter Zijlstra
c82513e513 sched: Change rq->nr_running to unsigned int
Since there's a PID space limit of 30bits (see
futex.h:FUTEX_TID_MASK) and allocating that many tasks (assuming a
lower bound of 2 pages per task) would still take 8T of memory it
seems reasonable to say that unsigned int is sufficient for
rq->nr_running.

When we do get anywhere near that amount of tasks I suspect other
things would go funny, load-balancer load computations would really
need to be hoisted to 128bit etc.

So save a few bytes and convert rq->nr_running and friends to
unsigned int.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-y3tvyszjdmbibade5bw8zl81@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-09 15:00:49 +02:00
Igor Mammedov
30b4e9eb78 sched: Fix KVM and ia64 boot crash due to sched_groups circular linked list assumption
If we have one cpu that failed to boot and boot cpu gave up on
waiting for it and then another cpu is being booted, kernel
might crash with following OOPS:

   BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
   IP: [<ffffffff812c3630>] __bitmap_weight+0x30/0x80
   Call Trace:
       [<ffffffff8108b9b6>] build_sched_domains+0x7b6/0xa50

The crash happens in init_sched_groups_power() that expects
sched_groups to be circular linked list. However it is not
always true, since sched_groups preallocated in __sdt_alloc are
initialized in build_sched_groups and it may exit early

        if (cpu != cpumask_first(sched_domain_span(sd)))
                return 0;

without initializing sd->groups->next field.

Fix bug by initializing next field right after sched_group was
allocated.

Also-Reported-by: Jiang Liu <liuj97@gmail.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Cc: a.p.zijlstra@chello.nl
Cc: pjt@google.com
Cc: seto.hidetoshi@jp.fujitsu.com
Link: http://lkml.kernel.org/r/1336559908-32533-1-git-send-email-imammedo@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-09 12:27:35 +02:00
Thomas Gleixner
67ba5293f7 Merge branch 'smp/threadalloc' into smp/hotplug
Reason: Pull in the separate branch which was created so arch/tile can
base further work on it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2012-05-08 14:07:48 +02:00
Hiroshi Shimamoto
489a71b029 sched: Update documentation and comments
Change sched_*.c to sched/*.c in documentation and comments.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4F795CAC.9080206@ct.jp.nec.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-07 15:04:18 +02:00
Ingo Molnar
436281c9a1 Merge branch 'linus' into sched/core
Merge reason: We were on a pretty old base, refresh before moving on.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-05-07 15:03:42 +02:00
Thomas Gleixner
a4a2eb490e init_task: Create generic init_task instance
All archs define init_task in the same way (except ia64, but there is
no particular reason why ia64 cannot use the common version). Create a
generic instance so all archs can be converted over.

The config switch is temporary and will be removed when all archs are
converted over.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Howells <dhowells@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Mark Salter <msalter@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/20120503085034.092585287@linutronix.de
2012-05-05 13:00:21 +02:00
Eric W. Biederman
9c806aa06f userns: Convert sched_set_affinity and sched_set_scheduler's permission checks
- Compare kuids with uid_eq
- kuid are uniuqe across all user namespaces so there is no longer the
  need for a user_namespace comparison.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2012-05-03 03:28:39 -07:00
Paul E. McKenney
616c310e83 rcu: Move PREEMPT_RCU preemption to switch_to() invocation
Currently, PREEMPT_RCU readers are enqueued upon entry to the scheduler.
This is inefficient because enqueuing is required only if there is a
context switch, and entry to the scheduler does not guarantee a context
switch.

The commit therefore moves the enqueuing to immediately precede the
call to switch_to() from the scheduler.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-02 14:43:23 -07:00
he, bo
fb2cf2c660 sched: Fix OOPS when build_sched_domains() percpu allocation fails
Under extreme memory used up situations, percpu allocation
might fail. We hit it when system goes to suspend-to-ram,
causing a kworker panic:

 EIP: [<c124411a>] build_sched_domains+0x23a/0xad0
 Kernel panic - not syncing: Fatal exception
 Pid: 3026, comm: kworker/u:3
 3.0.8-137473-gf42fbef #1

 Call Trace:
  [<c18cc4f2>] panic+0x66/0x16c
  [...]
  [<c1244c37>] partition_sched_domains+0x287/0x4b0
  [<c12a77be>] cpuset_update_active_cpus+0x1fe/0x210
  [<c123712d>] cpuset_cpu_inactive+0x1d/0x30
  [...]

With this fix applied build_sched_domains() will return -ENOMEM and
the suspend attempt fails.

Signed-off-by: he, bo <bo.he@intel.com>
Reviewed-by: Zhang, Yanmin <yanmin.zhang@intel.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/1335355161.5892.17.camel@hebo
[ So, we fail to deallocate a CPU because we cannot allocate RAM :-/
  I don't like that kind of sad behavior but nevertheless it should
  not crash under high memory load. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-04-26 12:54:53 +02:00
Peter Zijlstra
eb95308ee2 sched: Fix more load-balancing fallout
Commits 367456c756 ("sched: Ditch per cgroup task lists for
load-balancing") and 5d6523ebd ("sched: Fix load-balance wreckage")
left some more wreckage.

By setting loop_max unconditionally to ->nr_running load-balancing
could take a lot of time on very long runqueues (hackbench!). So keep
the sysctl as max limit of the amount of tasks we'll iterate.

Furthermore, the min load filter for migration completely fails with
cgroups since inequality in per-cpu state can easily lead to such
small loads :/

Furthermore the change to add new tasks to the tail of the queue
instead of the head seems to have some effect.. not quite sure I
understand why.

Combined these fixes solve the huge hackbench regression reported by
Tim when hackbench is ran in a cgroup.

Reported-by: Tim Chen <tim.c.chen@linux.intel.com>
Acked-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1335365763.28150.267.camel@twins
[ got rid of the CONFIG_PREEMPT tuning and made small readability edits ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-04-26 12:54:52 +02:00
Thomas Gleixner
29d5e0476e smp: Provide generic idle thread allocation
All SMP architectures have magic to fork the idle task and to store it
for reusage when cpu hotplug is enabled. Provide a generic
infrastructure for it.

Create/reinit the idle thread for the cpu which is brought up in the
generic code and hand the thread pointer to the architecture code via
__cpu_up().

Note, that fork_idle() is called via a workqueue, because this
guarantees that the idle thread does not get a reference to a user
space VM. This can happen when the boot process did not bring up all
possible cpus and a later cpu_up() is initiated via the sysfs
interface. In that case fork_idle() would be called in the context of
the user space task and take a reference on the user space VM.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: David Howells <dhowells@redhat.com>
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: x86@kernel.org
Acked-by: Venkatesh Pallipadi <venki@google.com>
Link: http://lkml.kernel.org/r/20120420124557.102478630@linutronix.de
2012-04-26 12:06:09 +02:00
Ingo Molnar
4cbb62148c Merge branch 'tip/sched/core' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace into sched/core
Pull a scheduler optimization commit from Steven Rostedt.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-04-14 15:12:04 +02:00
Kirill Tkhai
8d3d5ada56 sched_rt: Avoid unnecessary dequeue and enqueue of pushable tasks in set_cpus_allowed_rt()
Migration status depends on a difference of weight from 0 and 1.
If weight > 1 (<= 1) and old weight <= 1 (> 1) then task becomes
pushable (or not pushable). We are not insterested in its exact
values, is it 3 or 4, for example.
Now if we are changing affinity from a set of 3 cpus to a set of 4, the-
task will be dequeued and enqueued sequentially without important
difference in comparison with initial state. The only difference is in
internal representation of plist queue of pushable tasks and the fact
that the task may won't be the first in a sequence of the same priority
tasks. But it seems to me it gives nothing.

Link: http://lkml.kernel.org/r/273741334120764@web83.yandex.ru

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Tkhai Kirill <tkhai@yandex.ru>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2012-04-12 16:59:37 -04:00
Eric W. Biederman
c4a4d60379 userns: Use cred->user_ns instead of cred->user->user_ns
Optimize performance and prepare for the removal of the user_ns reference
from user_struct.  Remove the slow long walk through cred->user->user_ns and
instead go straight to cred->user_ns.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2012-04-07 16:55:51 -07:00
Tejun Heo
4baf6e3325 cgroup: convert all non-memcg controllers to the new cftype interface
Convert debug, freezer, cpuset, cpu_cgroup, cpuacct, net_prio, blkio,
net_cls and device controllers to use the new cftype based interface.
Termination entry is added to cftype arrays and populate callbacks are
replaced with cgroup_subsys->base_cftypes initializations.

This is functionally identical transformation.  There shouldn't be any
visible behavior change.

memcg is rather special and will be converted separately.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <paul@paulmenage.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Vivek Goyal <vgoyal@redhat.com>
2012-04-01 12:09:55 -07:00
Linus Torvalds
f22e08a79f Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar.

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Fix incorrect usage of for_each_cpu_mask() in select_fallback_rq()
  sched: Fix __schedule_bug() output when called from an interrupt
  sched/arch: Introduce the finish_arch_post_lock_switch() scheduler callback
2012-03-31 13:35:31 -07:00
Srivatsa S. Bhat
e3831edd59 sched: Fix incorrect usage of for_each_cpu_mask() in select_fallback_rq()
The function for_each_cpu_mask() expects a *pointer* to struct
cpumask as its second argument, whereas select_fallback_rq()
passes the value itself.

And moreover, for_each_cpu_mask() has been marked as obselete
in include/linux/cpumask.h. So move to the more appropriate
for_each_cpu() variant.

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Dave Jones <davej@redhat.com>
Cc: Liu Chuansheng <chuansheng.liu@intel.com>
Cc: vapier@gentoo.org
Cc: rusty@rustcorp.com.au
Link: http://lkml.kernel.org/r/4F75BED4.9050005@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-03-31 10:43:36 +02:00
Linus Torvalds
7fda0412c5 Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar.

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpusets: Remove an unused variable
  sched/rt: Improve pick_next_highest_task_rt()
  sched: Fix select_fallback_rq() vs cpu_active/cpu_online
  sched/x86/smp: Do not enable IRQs over calibrate_delay()
  sched: Fix compiler warning about declared inline after use
  MAINTAINERS: Update email address for SCHEDULER and PERF EVENTS
2012-03-29 14:46:05 -07:00
Ingo Molnar
1f56ee7b68 Merge branch 'sched/arch' into sched/urgent
Merge reason: It has not gone upstream via the ARM tree, merge it via
              the scheduler tree.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-29 12:48:22 +02:00
Stephen Boyd
6135fc1eb4 sched: Fix __schedule_bug() output when called from an interrupt
If schedule is called from an interrupt handler __schedule_bug()
will call show_regs() with the registers saved during the
interrupt handling done in do_IRQ(). This means we'll see the
registers and the backtrace for the process that was interrupted
and not the full backtrace explaining who called schedule().

This is due to 838225b ("sched: use show_regs() to improve
__schedule_bug() output", 2007-10-24) which improperly assumed
that get_irq_regs() would return the registers for the current
stack because it is being called from within an interrupt
handler. Simply remove the show_reg() code so that we dump a
backtrace for the interrupt handler that called schedule().

[ I ran across this when I was presented with a scheduling while
  atomic log with a stacktrace pointing at spin_unlock_irqrestore().
  It made no sense and I had to guess what interrupt handler could
  be called and poke around for someone calling schedule() in an
  interrupt handler. A simple test of putting an msleep() in
  an interrupt handler works better with this patch because you
  can actually see the msleep() call in the backtrace. ]

Also-reported-by: Chris Metcalf <cmetcalf@tilera.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Satyam Sharma <satyam@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1332979847-27102-1-git-send-email-sboyd@codeaurora.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-03-29 08:34:45 +02:00
David Howells
96f951edb1 Add #includes needed to permit the removal of asm/system.h
asm/system.h is a cause of circular dependency problems because it contains
commonly used primitive stuff like barrier definitions and uncommonly used
stuff like switch_to() that might require MMU definitions.

asm/system.h has been disintegrated by this point on all arches into the
following common segments:

 (1) asm/barrier.h

     Moved memory barrier definitions here.

 (2) asm/cmpxchg.h

     Moved xchg() and cmpxchg() here.  #included in asm/atomic.h.

 (3) asm/bug.h

     Moved die() and similar here.

 (4) asm/exec.h

     Moved arch_align_stack() here.

 (5) asm/elf.h

     Moved AT_VECTOR_SIZE_ARCH here.

 (6) asm/switch_to.h

     Moved switch_to() here.

Signed-off-by: David Howells <dhowells@redhat.com>
2012-03-28 18:30:03 +01:00
Michael J Wang
1b028abc77 sched/rt: Improve pick_next_highest_task_rt()
Avoid extra work by continuing on to the next rt_rq if the highest
prio task in current rt_rq is the same priority as our candidate
task.

More detailed explanation:  if next is not NULL, then we have found a
candidate task, and its priority is next->prio.  Now we are looking
for an even higher priority task in the other rt_rq's.  idx is the
highest priority in the current candidate rt_rq.  In the current 3.3
code, if idx is equal to next->prio, we would start scanning the tasks
in that rt_rq and replace the current candidate task with a task from
that rt_rq.  But the new task would only have a priority that is equal
to our previous candidate task, so we have not advanced our goal of
finding a higher prio task.  So we should avoid the extra work by
continuing on to the next rt_rq if idx is equal to next->prio.

Signed-off-by: Michael J Wang <mjwang@broadcom.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/2EF88150C0EF2C43A218742ED384C1BC0FC83D6B@IRVEXCHMB08.corp.ad.broadcom.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-03-27 14:52:12 +02:00
Peter Zijlstra
2baab4e904 sched: Fix select_fallback_rq() vs cpu_active/cpu_online
Commit 5fbd036b55 ("sched: Cleanup cpu_active madness"), which was
supposed to finally sort the cpu_active mess, instead uncovered more.

Since CPU_STARTING is ran before setting the cpu online, there's a
(small) window where the cpu has active,!online.

If during this time there's a wakeup of a task that used to reside on
that cpu select_task_rq() will use select_fallback_rq() to compute an
alternative cpu to run on since we find !online.

select_fallback_rq() however will compute the new cpu against
cpu_active, this means that it can return the same cpu it started out
with, the !online one, since that cpu is in fact marked active.

This results in us trying to scheduling a task on an offline cpu and
triggering a WARN in the IPI code.

The solution proposed by Chuansheng Liu of setting cpu_active in
set_cpu_online() is buggy, firstly not all archs actually use
set_cpu_online(), secondly, not all archs call set_cpu_online() with
IRQs disabled, this means we would introduce either the same race or
the race from fd8a7de17 ("x86: cpu-hotplug: Prevent softirq wakeup on
wrong CPU") -- albeit much narrower.

[ By setting online first and active later we have a window of
  online,!active, fresh and bound kthreads have task_cpu() of 0 and
  since cpu0 isn't in tsk_cpus_allowed() we end up in
  select_fallback_rq() which excludes !active, resulting in a reset
  of ->cpus_allowed and the thread running all over the place. ]

The solution is to re-work select_fallback_rq() to require active
_and_ online. This makes the active,!online case work as expected,
OTOH archs running CPU_STARTING after setting online are now
vulnerable to the issue from fd8a7de17 -- these are alpha and
blackfin.

Reported-by: Chuansheng Liu <chuansheng.liu@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: linux-alpha@vger.kernel.org
Link: http://lkml.kernel.org/n/tip-hubqk1i10o4dpvlm06gq7v6j@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-03-27 14:50:14 +02:00
Peter Zijlstra
6c16a6dcb0 sched: Fix compiler warning about declared inline after use
kernel/sched/fair.c:420: warning: 'account_cfs_rq_runtime' declared inline after being called
kernel/sched/fair.c:420: warning: previous declaration of 'account_cfs_rq_runtime' was here
kernel/sched/fair.c:1165: warning: 'return_cfs_rq_runtime' declared inlineafter being called
kernel/sched/fair.c:1165: warning: previous declaration of 'return_cfs_rq_runtime' was here

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20120321200717.49BB4A024E@akpm.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-03-23 10:39:28 +01:00
Linus Torvalds
3556485f15 Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
Pull security subsystem updates for 3.4 from James Morris:
 "The main addition here is the new Yama security module from Kees Cook,
  which was discussed at the Linux Security Summit last year.  Its
  purpose is to collect miscellaneous DAC security enhancements in one
  place.  This also marks a departure in policy for LSM modules, which
  were previously limited to being standalone access control systems.
  Chromium OS is using Yama, and I believe there are plans for Ubuntu,
  at least.

  This patchset also includes maintenance updates for AppArmor, TOMOYO
  and others."

Fix trivial conflict in <net/sock.h> due to the jumo_label->static_key
rename.

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (38 commits)
  AppArmor: Fix location of const qualifier on generated string tables
  TOMOYO: Return error if fails to delete a domain
  AppArmor: add const qualifiers to string arrays
  AppArmor: Add ability to load extended policy
  TOMOYO: Return appropriate value to poll().
  AppArmor: Move path failure information into aa_get_name and rename
  AppArmor: Update dfa matching routines.
  AppArmor: Minor cleanup of d_namespace_path to consolidate error handling
  AppArmor: Retrieve the dentry_path for error reporting when path lookup fails
  AppArmor: Add const qualifiers to generated string tables
  AppArmor: Fix oops in policy unpack auditing
  AppArmor: Fix error returned when a path lookup is disconnected
  KEYS: testing wrong bit for KEY_FLAG_REVOKED
  TOMOYO: Fix mount flags checking order.
  security: fix ima kconfig warning
  AppArmor: Fix the error case for chroot relative path name lookup
  AppArmor: fix mapping of META_READ to audit and quiet flags
  AppArmor: Fix underflow in xindex calculation
  AppArmor: Fix dropping of allowed operations that are force audited
  AppArmor: Add mising end of structure test to caps unpacking
  ...
2012-03-21 13:25:04 -07:00
Linus Torvalds
0d9cabdcce Merge branch 'for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup changes from Tejun Heo:
 "Out of the 8 commits, one fixes a long-standing locking issue around
  tasklist walking and others are cleanups."

* 'for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: Walk task list under tasklist_lock in cgroup_enable_task_cg_list
  cgroup: Remove wrong comment on cgroup_enable_task_cg_list()
  cgroup: remove cgroup_subsys argument from callbacks
  cgroup: remove extra calls to find_existing_css_set
  cgroup: replace tasklist_lock with rcu_read_lock
  cgroup: simplify double-check locking in cgroup_attach_proc
  cgroup: move struct cgroup_pidlist out from the header file
  cgroup: remove cgroup_attach_task_current_cg()
2012-03-20 18:11:21 -07:00
Linus Torvalds
2ba68940c8 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler changes for v3.4 from Ingo Molnar

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
  printk: Make it compile with !CONFIG_PRINTK
  sched/x86: Fix overflow in cyc2ns_offset
  sched: Fix nohz load accounting -- again!
  sched: Update yield() docs
  printk/sched: Introduce special printk_sched() for those awkward moments
  sched/nohz: Correctly initialize 'next_balance' in 'nohz' idle balancer
  sched: Cleanup cpu_active madness
  sched: Fix load-balance wreckage
  sched: Clean up parameter passing of proc_sched_autogroup_set_nice()
  sched: Ditch per cgroup task lists for load-balancing
  sched: Rename load-balancing fields
  sched: Move load-balancing arguments into helper struct
  sched/rt: Do not submit new work when PI-blocked
  sched/rt: Prevent idle task boosting
  sched/wait: Add __wake_up_all_locked() API
  sched/rt: Document scheduler related skip-resched-check sites
  sched/rt: Use schedule_preempt_disabled()
  sched/rt: Add schedule_preempt_disabled()
  sched/rt: Do not throttle when PI boosting
  sched/rt: Keep period timer ticking when rt throttling is active
  ...
2012-03-20 10:31:44 -07:00
Catalin Marinas
01f23e1630 sched/arch: Introduce the finish_arch_post_lock_switch() scheduler callback
This callback is called by the scheduler after rq->lock has been released
and interrupts enabled. It will be used in subsequent patches on the ARM
architecture.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Frank Rowand <frank.rowand@am.sony.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Tested-by: Marc Zyngier <Marc.Zyngier@arm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/20120313110840.7b444deb6b1bb902c15f3cdf@canb.auug.org.au
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13 10:17:45 +01:00
Peter Zijlstra
c308b56b53 sched: Fix nohz load accounting -- again!
Various people reported nohz load tracking still being wrecked, but Doug
spotted the actual problem. We fold the nohz remainder in too soon,
causing us to loose samples and under-account.

So instead of playing catch-up up-front, always do a single load-fold
with whatever state we encounter and only then fold the nohz remainder
and play catch-up.

Reported-by: Doug Smythies <dsmythies@telus.net>
Reported-by: LesÅ=82aw Kope=C4=87 <leslaw.kopec@nasza-klasa.pl>
Reported-by: Aman Gupta <aman@tmm1.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-4v31etnhgg9kwd6ocgx3rxl8@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-12 20:43:17 +01:00
Peter Zijlstra
8e3fabfde4 sched: Update yield() docs
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1331056466.11248.327.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-12 20:43:17 +01:00
Peter Zijlstra
3ccf3e8306 printk/sched: Introduce special printk_sched() for those awkward moments
There's a few awkward printk()s inside of scheduler guts that people
prefer to keep but really are rather deadlock prone. Fudge around it
by storing the text in a per-cpu buffer and poll it using the existing
printk_tick() handler.

This will drop output when its more frequent than once a tick, however
only the affinity thing could possible go that fast and for that just
one should suffice to notify the admin he's done something silly..

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-wua3lmkt3dg8nfts66o6brne@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-12 20:43:16 +01:00
Diwakar Tundlam
554cecaf73 sched/nohz: Correctly initialize 'next_balance' in 'nohz' idle balancer
The 'next_balance' field of 'nohz' idle balancer must be initialized
to jiffies. Since jiffies is initialized to negative 300 seconds the
'nohz' idle balancer does not run for the first 300s (5mins) after
bootup. If no new processes are spawed or no idle cycles happen, the
load on the cpus will remain unbalanced for that duration.

Signed-off-by: Diwakar Tundlam <dtundlam@nvidia.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1DD7BFEDD3147247B1355BEFEFE4665237994F30EF@HQMAIL04.nvidia.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-12 20:43:16 +01:00
Peter Zijlstra
5fbd036b55 sched: Cleanup cpu_active madness
Stepan found:

CPU0		CPUn

_cpu_up()
  __cpu_up()

		boostrap()
		  notify_cpu_starting()
		  set_cpu_online()
		  while (!cpu_active())
		    cpu_relax()

<PREEMPT-out>

smp_call_function(.wait=1)
  /* we find cpu_online() is true */
  arch_send_call_function_ipi_mask()

  /* wait-forever-more */

<PREEMPT-in>
		  local_irq_enable()

  cpu_notify(CPU_ONLINE)
    sched_cpu_active()
      set_cpu_active()

Now the purpose of cpu_active is mostly with bringing down a cpu, where
we mark it !active to avoid the load-balancer from moving tasks to it
while we tear down the cpu. This is required because we only update the
sched_domain tree after we brought the cpu-down. And this is needed so
that some tasks can still run while we bring it down, we just don't want
new tasks to appear.

On cpu-up however the sched_domain tree doesn't yet include the new cpu,
so its invisible to the load-balancer, regardless of the active state.
So instead of setting the active state after we boot the new cpu (and
consequently having to wait for it before enabling interrupts) set the
cpu active before we set it online and avoid the whole mess.

Reported-by: Stepan Moskovchenko <stepanm@codeaurora.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1323965362.18942.71.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-12 20:43:15 +01:00
Peter Zijlstra
5d6523ebd2 sched: Fix load-balance wreckage
Commit 367456c ("sched: Ditch per cgroup task lists for
load-balancing") completely wrecked load-balancing due to
a few silly mistakes.

Correct those and remove more pointless code.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-zk04ihygwxn7qqrlpaf73b0r@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-12 20:43:15 +01:00
Linus Torvalds
4293f20c19 Revert "CPU hotplug, cpusets, suspend: Don't touch cpusets during suspend/resume"
This reverts commit 8f2f748b06.

It causes some odd regression that we have not figured out, and it's too
late in the -rc series to try to figure it out now.

As reported by Konstantin Khlebnikov, it causes consistent hangs on his
laptop (Thinkpad x220: 2x cores + HT).  They can be avoided by adding
calls to "rebuild_sched_domains();" in cpuset_cpu_[in]active() for the
CPU_{ONLINE/DOWN_FAILED/DOWN_PREPARE}_FROZEN cases, but it's not at all
clear why, and it makes no sense.

Konstantin's config doesn't even have CONFIG_CPUSETS enabled, just to
make things even more interesting.  So it's not the cpusets, it's just
the scheduling domains.

So until this is understood, revert.

Bisected-reported-and-tested-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-07 08:21:19 -08:00
Ingo Molnar
737f24bda7 Merge branch 'perf/urgent' into perf/core
Conflicts:
	tools/perf/builtin-record.c
	tools/perf/builtin-top.c
	tools/perf/perf.h
	tools/perf/util/top.h

Merge reason: resolve these cherry-picking conflicts.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-05 09:20:08 +01:00
Hiroshi Shimamoto
2e5b5b3a1b sched: Clean up parameter passing of proc_sched_autogroup_set_nice()
Pass nice as a value to proc_sched_autogroup_set_nice().

No side effect is expected, and the variable err will be overwritten with
the return value.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4F45FBB7.5090607@ct.jp.nec.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-02 12:23:49 +01:00
Peter Zijlstra
367456c756 sched: Ditch per cgroup task lists for load-balancing
Per cgroup load-balance has numerous problems, chief amongst them that
there is no real sane order in them. So stop pretending it makes sense
and enqueue all tasks on a single list.

This also allows us to more easily fix the fwd progress issue
uncovered by the lock-break stuff. Rotate the list on failure to
migreate and limit the total iterations to nr_running (which with
releasing the lock isn't strictly accurate but close enough).

Also add a filter that skips very light tasks on the first attempt
around the list, this attempts to avoid shooting whole cgroups around
without affecting over balance.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: pjt@google.com
Link: http://lkml.kernel.org/n/tip-tx8yqydc7eimgq7i4rkc3a4g@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 13:08:37 +01:00
Peter Zijlstra
ddcdf6e7d9 sched: Rename load-balancing fields
s/env->this_/env->dst_/g
 s/env->busiest_/env->src_/g
 s/pull_task/move_task/g

Makes everything clearer.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: pjt@google.com
Link: http://lkml.kernel.org/n/tip-0yvgms8t8x962drpvl0fu0kk@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 10:51:23 +01:00
Peter Zijlstra
8e45cb545d sched: Move load-balancing arguments into helper struct
Passing large sets of similar arguments all around the load-balancer
gets tiresom when you want to modify something. Stick them all in a
helper structure and pass the structure around.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: pjt@google.com
Link: http://lkml.kernel.org/n/tip-5slqz0vhsdzewrfk9eza1aon@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 10:51:22 +01:00
Thomas Gleixner
3c7d51843b sched/rt: Do not submit new work when PI-blocked
When we are PI-blocked then we want to get things done ASAP.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-vw8et3445km5b8mpihf4trae@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 10:46:54 +01:00
Thomas Gleixner
1c4dd99bed sched/rt: Prevent idle task boosting
Idle task boosting is a nono in general. There is one
exception, when PREEMPT_RT and NOHZ is active:

The idle task calls get_next_timer_interrupt() and holds
the timer wheel base->lock on the CPU and another CPU wants
to access the timer (probably to cancel it). We can safely
ignore the boosting request, as the idle CPU runs this code
with interrupts disabled and will complete the lock
protected section without being interrupted. So there is no
real need to boost.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-755rvsosz7sdzot12a3gbha6@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 10:28:05 +01:00
Thomas Gleixner
63b2001169 sched/wait: Add __wake_up_all_locked() API
For code which protects the waitqueue itself with another lock it
makes no sense to acquire the waitqueue lock for wakeup all. Provide
__wake_up_all_locked().

This is an optimization on the vanilla kernel (to be used by the
PCI code) and an important semantic distinction on -rt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-ux6m4b8jonb9inx8xafh77ds@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 10:28:04 +01:00
Thomas Gleixner
ba74c1448f sched/rt: Document scheduler related skip-resched-check sites
Create a distinction between scheduler related preempt_enable_no_resched()
calls and the nearly one hundred other places in the kernel that do not
want to reschedule, for one reason or another.

This distinction matters for -rt, where the scheduler and the non-scheduler
preempt models (and checks) are different. For upstream it's purely
documentational.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/n/tip-gs88fvx2mdv5psnzxnv575ke@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 10:28:04 +01:00
Thomas Gleixner
c5491ea779 sched/rt: Add schedule_preempt_disabled()
Add helper to get rid of the ever repeating:

    preempt_enable_no_resched();
    schedule();
    preempt_disable();

patterns.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-wxx7btox7coby6ifv5vzhzgp@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 10:28:03 +01:00
Peter Zijlstra
7abc63b1bd sched/rt: Do not throttle when PI boosting
When a runqueue has rt_runtime_us = 0 then the only way it can
accumulate rt_time is via PI boosting. That causes the runqueue
to be throttled and replenishing does not change anything due to
rt_runtime_us = 0. So avoid that situation by clearing rt_time and
skip the throttling alltogether.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
[ Changelog ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/n/tip-7x70cypsotjb4jvcor3edctk@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 10:28:02 +01:00
Peter Zijlstra
42c62a589f sched/rt: Keep period timer ticking when rt throttling is active
When a runqueue is throttled we cannot disable the period timer
because that timer is the only way to undo the throttling.

We got stale throttling entries when a rq was throttled and then the
global sysctl was disabled, which stopped the timer.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
[ Added changelog ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/n/tip-nuj34q52p6ro7szapuz84i0v@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 10:28:01 +01:00
Ingo Molnar
7e4d960993 Merge branch 'linus' into sched/core
Merge reason: we'll queue up dependent patches.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-01 10:26:43 +01:00
Srivatsa S. Bhat
8f2f748b06 CPU hotplug, cpusets, suspend: Don't touch cpusets during suspend/resume
Currently, during CPU hotplug, the cpuset callbacks modify the cpusets
to reflect the state of the system, and this handling is asymmetric.
That is, upon CPU offline, that CPU is removed from all cpusets. However
when it comes back online, it is put back only to the root cpuset.

This gives rise to a significant problem during suspend/resume. During
suspend, we offline all non-boot cpus and during resume we online them back.
Which means, after a resume, all cpusets (except the root cpuset) will be
restricted to just one single CPU (the boot cpu). But the whole point of
suspend/resume is to restore the system to a state which is as close as
possible to how it was before suspend.

So to fix this, don't touch cpusets during suspend/resume. That is, modify
the cpuset-related CPU hotplug callback to just ignore CPU hotplug when it
is initiated as part of the suspend/resume sequence.

Reported-by: Prashanth Nageshappa <prashanth@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/4F460D7B.1020703@linux.vnet.ibm.com
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-27 11:38:13 +01:00
Ingo Molnar
c5905afb0e static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_slow_[inc|dec]()
So here's a boot tested patch on top of Jason's series that does
all the cleanups I talked about and turns jump labels into a
more intuitive to use facility. It should also address the
various misconceptions and confusions that surround jump labels.

Typical usage scenarios:

        #include <linux/static_key.h>

        struct static_key key = STATIC_KEY_INIT_TRUE;

        if (static_key_false(&key))
                do unlikely code
        else
                do likely code

Or:

        if (static_key_true(&key))
                do likely code
        else
                do unlikely code

The static key is modified via:

        static_key_slow_inc(&key);
        ...
        static_key_slow_dec(&key);

The 'slow' prefix makes it abundantly clear that this is an
expensive operation.

I've updated all in-kernel code to use this everywhere. Note
that I (intentionally) have not pushed through the rename
blindly through to the lowest levels: the actual jump-label
patching arch facility should be named like that, so we want to
decouple jump labels from the static-key facility a bit.

On non-jump-label enabled architectures static keys default to
likely()/unlikely() branches.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jason Baron <jbaron@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: a.p.zijlstra@chello.nl
Cc: mathieu.desnoyers@efficios.com
Cc: davem@davemloft.net
Cc: ddaney.cavm@gmail.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20120222085809.GA26397@elte.hu
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-24 10:05:59 +01:00
Hiroshi Shimamoto
de5bdff7a7 sched: Make initial SCHED_RR timeslace DEF_TIMESLICE
Current the initial SCHED_RR timeslice of init_task is HZ, which means
1s, and is not same as the default SCHED_RR timeslice DEF_TIMESLICE.

Change that initial timeslice to the DEF_TIMESLICE.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
[ s/DEF_TIMESLICE/RR_TIMESLICE/g ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4F3C9995.3010800@ct.jp.nec.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-22 12:28:29 +01:00
Nikunj A. Dadhania
62f6536a63 sched: Remove rcu_read_lock/unlock() from select_idle_sibling()
select_idle_sibling() is called from select_task_rq_fair(), which
already has the RCU read lock held.

Signed-off-by: Nikunj A. Dadhania <nikunj@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120217030409.11748.12491.stgit@abhimanyu
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-22 12:28:28 +01:00
Peter Zijlstra
8c79a045fd sched/events: Revert trace_sched_stat_sleeptime()
Commit 1ac9bc69 ("sched/tracing: Add a new tracepoint for sleeptime")
added a new sched:sched_stat_sleeptime tracepoint.

It's broken: the first sample we get on a task might be bad because
of a stale sleep_start value that wasn't reset at the last task switch
because the tracepoint was not active.

It also breaks the existing schedstat samples due to the side
effects of:

-               se->statistics.sleep_start = 0;
...
-               se->statistics.block_start = 0;

Nor do I see means to fix it without adding overhead to the scheduler
fast path, which I'm not willing to for the sake of redundant
instrumentation.

Most importantly, sleep time information can already be constructed
by tracing context switches and wakeups, and taking the timestamp
difference between the schedule-out, the wakeup and the schedule-in.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/n/tip-pc4c9qhl8q6vg3bs4j6k0rbd@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-22 12:06:55 +01:00
Al Viro
4040153087 security: trim security.h
Trim security.h

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: James Morris <jmorris@namei.org>
2012-02-14 10:45:42 +11:00
Li Zefan
761b3ef50e cgroup: remove cgroup_subsys argument from callbacks
The argument is not used at all, and it's not necessary, because
a specific callback handler of course knows which subsys it
belongs to.

Now only ->pupulate() takes this argument, because the handlers of
this callback always call cgroup_add_file()/cgroup_add_files().

So we reduce a few lines of code, though the shrinking of object size
is minimal.

 16 files changed, 113 insertions(+), 162 deletions(-)

   text    data     bss     dec     hex filename
5486240  656987 7039960 13183187         c928d3 vmlinux.o.orig
5486170  656987 7039960 13183117         c9288d vmlinux.o

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2012-02-02 09:20:22 -08:00
Hiroshi Shimamoto
ed387b781e sched: Move SMP-only variable into the SMP section
This also fixes the following compilation warning on !SMP:

  CC kernel/sched/fair.o
  kernel/sched/fair.c:218:36: warning: 'max_load_balance_interval' defined but not used [-Wunused-variable]

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4F2754A0.9090306@ct.jp.nec.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-01-31 13:40:59 +01:00
Rakib Mullick
30fd049afc sched: Remove sched_switch
Currently we don't utilize the sched_switch field anymore.

But, simply removing sched_switch field from the middle of the
sched_stat output will break tools.

So, to stay compatible we hardcode it to zero and remove the
field from the scheduler data structures.

Update the schedstat documentation accordingly.

Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1327422836.27181.5.camel@localhost.localdomain
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-01-27 13:28:53 +01:00
Vincent Guittot
4ec4412e1e sched: Ensure cpu_power periodic update
With a lot of small tasks, the softirq sched is nearly never called
when no_hz is enabled. In this case load_balance() is mainly called
with the newly_idle mode which doesn't update the cpu_power.

Add a next_update field which ensure a maximum update period when
there is short activity.

Having stale cpu_power information can skew the load-balancing
decisions, this is cured by the guaranteed update.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1323717668-2143-1-git-send-email-vincent.guittot@linaro.org
2012-01-27 13:28:49 +01:00
Peter Zijlstra
39be350127 sched, block: Unify cache detection
The block layer has some code trying to determine if two CPUs share a
cache, the scheduler has a similar function. Expose the function used
by the scheduler and make the block layer use it, thereby removing the
block layers usage of CONFIG_SCHED* and topology bits.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Jens Axboe <axboe@kernel.dk>
Link: http://lkml.kernel.org/r/1327579450.2446.95.camel@twins
2012-01-27 13:28:48 +01:00
Chanho Min
cb297a3e43 sched/rt: Fix task stack corruption under __ARCH_WANT_INTERRUPTS_ON_CTXSW
This issue happens under the following conditions:

 1. preemption is off
 2. __ARCH_WANT_INTERRUPTS_ON_CTXSW is defined
 3. RT scheduling class
 4. SMP system

Sequence is as follows:

 1.suppose current task is A. start schedule()
 2.task A is enqueued pushable task at the entry of schedule()
   __schedule
    prev = rq->curr;
    ...
    put_prev_task
     put_prev_task_rt
      enqueue_pushable_task
 4.pick the task B as next task.
   next = pick_next_task(rq);
 3.rq->curr set to task B and context_switch is started.
   rq->curr = next;
 4.At the entry of context_swtich, release this cpu's rq->lock.
   context_switch
    prepare_task_switch
     prepare_lock_switch
      raw_spin_unlock_irq(&rq->lock);
 5.Shortly after rq->lock is released, interrupt is occurred and start IRQ context
 6.try_to_wake_up() which called by ISR acquires rq->lock
    try_to_wake_up
     ttwu_remote
      rq = __task_rq_lock(p)
      ttwu_do_wakeup(rq, p, wake_flags);
        task_woken_rt
 7.push_rt_task picks the task A which is enqueued before.
   task_woken_rt
    push_rt_tasks(rq)
     next_task = pick_next_pushable_task(rq)
 8.At find_lock_lowest_rq(), If double_lock_balance() returns 0,
   lowest_rq can be the remote rq.
  (But,If preemption is on, double_lock_balance always return 1 and it
   does't happen.)
   push_rt_task
    find_lock_lowest_rq
     if (double_lock_balance(rq, lowest_rq))..
 9.find_lock_lowest_rq return the available rq. task A is migrated to
   the remote cpu/rq.
   push_rt_task
    ...
    deactivate_task(rq, next_task, 0);
    set_task_cpu(next_task, lowest_rq->cpu);
    activate_task(lowest_rq, next_task, 0);
 10. But, task A is on irq context at this cpu.
     So, task A is scheduled by two cpus at the same time until restore from IRQ.
     Task A's stack is corrupted.

To fix it, don't migrate an RT task if it's still running.

Signed-off-by: Chanho Min <chanho.min@lge.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/CAOAMb1BHA=5fm7KTewYyke6u-8DP0iUuJMpgQw54vNeXFsGpoQ@mail.gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-01-27 12:49:41 +01:00
Suresh Siddha
71325960d1 sched/nohz: Fix nohz cpu idle load balancing state with cpu hotplug
With the recent nohz scheduler changes, rq's nohz flag
'NOHZ_TICK_STOPPED' and its associated state doesn't get cleared
immediately after the cpu exits idle. This gets cleared as part
of the next tick seen on that cpu.

For the cpu offline support, we need to clear this state
manually. Fix it by registering a cpu notifier, which clears the
nohz idle load balance state for this rq explicitly during the
CPU_DYING notification.

There won't be any nohz updates for that cpu, after the
CPU_DYING notification. But lets be extra paranoid and skip
updating the nohz state in the select_nohz_load_balancer() if
the cpu is not in active state anymore.

Reported-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Reviewed-and-tested-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1327026538.16150.40.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-01-26 19:38:13 +01:00
Christian Borntraeger
db7e527da4 sched/s390: Fix compile error in sched/core.c
Commit 029632fbb7 ("sched: Make
separate sched*.c translation units") removed the include of
asm/mutex.h from sched.c.

This breaks the combination of:

 CONFIG_MUTEX_SPIN_ON_OWNER=yes
 CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX=yes

like s390 without mutex debugging:

  CC      kernel/sched/core.o
  kernel/sched/core.c: In function ‘mutex_spin_on_owner’:
  kernel/sched/core.c:3287: error: implicit declaration of function ‘arch_mutex_cpu_relax’

Lets re-add the include to kernel/sched/core.c

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1326268696-30904-1-git-send-email-borntraeger@de.ibm.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-01-26 19:38:11 +01:00
Peter Zijlstra
4ca9b72b71 sched: Fix rq->nr_uninterruptible update race
KOSAKI Motohiro noticed the following race:

 > CPU0                    CPU1
 > --------------------------------------------------------
 > deactivate_task()
 >                         task->state = TASK_UNINTERRUPTIBLE;
 > activate_task()
 >    rq->nr_uninterruptible--;
 >
 >                         schedule()
 >                           deactivate_task()
 >                             rq->nr_uninterruptible++;
 >

Kosaki-San's scenario is possible when CPU0 runs
__sched_setscheduler() against CPU1's current @task.

__sched_setscheduler() does a dequeue/enqueue in order to move
the task to its new queue (position) to reflect the newly provided
scheduling parameters. However it should be completely invariant to
nr_uninterruptible accounting, sched_setscheduler() doesn't affect
readyness to run, merely policy on when to run.

So convert the inappropriate activate/deactivate_task usage to
enqueue/dequeue_task, which avoids the nr_uninterruptible accounting.

Also convert the two other sites: __migrate_task() and
normalize_task() that still use activate/deactivate_task. These sites
aren't really a problem since __migrate_task() will only be called on
non-running task (and therefore are immume to the described problem)
and normalize_task() isn't ever used on regular systems.

Also remove the comments from activate/deactivate_task since they're
misleading at best.

Reported-by: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1327486224.2614.45.camel@laptop
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-01-26 19:38:09 +01:00
Randy Dunlap
fa757281a0 kernel-doc: fix kernel-doc warnings in sched
Fix new kernel-doc notation warnings:

Warning(include/linux/sched.h:2094): No description found for parameter 'p'
Warning(include/linux/sched.h:2094): Excess function parameter 'tsk' description in 'is_idle_task'
Warning(kernel/sched/cpupri.c:139): No description found for parameter 'newpri'
Warning(kernel/sched/cpupri.c:139): Excess function parameter 'pri' description in 'cpupri_set'
Warning(kernel/sched/cpupri.c:208): Excess function parameter 'bootmem' description in 'cpupri_init'

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Cc:	Ingo Molnar <mingo@elte.hu>
Cc:	Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-23 08:44:54 -08:00
Linus Torvalds
c49c41a413 Merge branch 'for-linus' of git://selinuxproject.org/~jmorris/linux-security
* 'for-linus' of git://selinuxproject.org/~jmorris/linux-security:
  capabilities: remove __cap_full_set definition
  security: remove the security_netlink_recv hook as it is equivalent to capable()
  ptrace: do not audit capability check when outputing /proc/pid/stat
  capabilities: remove task_ns_* functions
  capabitlies: ns_capable can use the cap helpers rather than lsm call
  capabilities: style only - move capable below ns_capable
  capabilites: introduce new has_ns_capabilities_noaudit
  capabilities: call has_ns_capability from has_capability
  capabilities: remove all _real_ interfaces
  capabilities: introduce security_capable_noaudit
  capabilities: reverse arguments to security_capable
  capabilities: remove the task from capable LSM hook entirely
  selinux: sparse fix: fix several warnings in the security server cod
  selinux: sparse fix: fix warnings in netlink code
  selinux: sparse fix: eliminate warnings for selinuxfs
  selinux: sparse fix: declare selinux_disable() in security.h
  selinux: sparse fix: move selinux_complete_init
  selinux: sparse fix: make selinux_secmark_refcount static
  SELinux: Fix RCU deref check warning in sel_netport_insert()

Manually fix up a semantic mis-merge wrt security_netlink_recv():

 - the interface was removed in commit fd77846152 ("security: remove
   the security_netlink_recv hook as it is equivalent to capable()")

 - a new user of it appeared in commit a38f7907b9 ("crypto: Add
   userspace configuration API")

causing no automatic merge conflict, but Eric Paris pointed out the
issue.
2012-01-14 18:36:33 -08:00
Linus Torvalds
b8bf17d311 Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Fix lockup by limiting load-balance retries on lock-break
  sched: Fix CONFIG_CGROUP_SCHED dependency
  sched: Remove empty #ifdefs
2012-01-11 22:52:48 -08:00
Peter Zijlstra
bced76aeac sched: Fix lockup by limiting load-balance retries on lock-break
Eric and David reported dead machines and traced it to commit
a195f004 ("sched: Fix load-balance lock-breaking"), it turns out
there's still a scenario where we can end up re-trying forever.

Since there is no strict forward progress guarantee in the
load-balance iteration we can get stuck re-retrying the same
task-set over and over.

Creating a forward progress guarantee with the existing
structure is somewhat non-trivial, for now simply terminate the
retry loop after a few tries.

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Reported-by: David Ahern <dsahern@gmail.com>
[ logic cleanup as suggested by Eric ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1326297936.2442.157.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-01-11 17:15:12 +01:00
Hiroshi Shimamoto
9b9fb610f6 sched: Remove empty #ifdefs
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4F0B8525.8070901@ct.jp.nec.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-01-10 09:57:41 +01:00
Linus Torvalds
db0c2bf69a Merge branch 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
* 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits)
  cgroup: fix to allow mounting a hierarchy by name
  cgroup: move assignement out of condition in cgroup_attach_proc()
  cgroup: Remove task_lock() from cgroup_post_fork()
  cgroup: add sparse annotation to cgroup_iter_start() and cgroup_iter_end()
  cgroup: mark cgroup_rmdir_waitq and cgroup_attach_proc() as static
  cgroup: only need to check oldcgrp==newgrp once
  cgroup: remove redundant get/put of task struct
  cgroup: remove redundant get/put of old css_set from migrate
  cgroup: Remove unnecessary task_lock before fetching css_set on migration
  cgroup: Drop task_lock(parent) on cgroup_fork()
  cgroups: remove redundant get/put of css_set from css_set_check_fetched()
  resource cgroups: remove bogus cast
  cgroup: kill subsys->can_attach_task(), pre_attach() and attach_task()
  cgroup, cpuset: don't use ss->pre_attach()
  cgroup: don't use subsys->can_attach_task() or ->attach_task()
  cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach()
  cgroup: improve old cgroup handling in cgroup_attach_proc()
  cgroup: always lock threadgroup during migration
  threadgroup: extend threadgroup_lock() to cover exit and exec
  threadgroup: rename signal->threadgroup_fork_lock to ->group_rwsem
  ...

Fix up conflict in kernel/cgroup.c due to commit e0197aae59: "cgroups:
fix a css_set not found bug in cgroup_attach_proc" that already
mentioned that the bug is fixed (differently) in Tejun's cgroup
patchset. This one, in other words.
2012-01-09 12:59:24 -08:00
Linus Torvalds
972b2c7199 Merge branch 'for-linus2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
* 'for-linus2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (165 commits)
  reiserfs: Properly display mount options in /proc/mounts
  vfs: prevent remount read-only if pending removes
  vfs: count unlinked inodes
  vfs: protect remounting superblock read-only
  vfs: keep list of mounts for each superblock
  vfs: switch ->show_options() to struct dentry *
  vfs: switch ->show_path() to struct dentry *
  vfs: switch ->show_devname() to struct dentry *
  vfs: switch ->show_stats to struct dentry *
  switch security_path_chmod() to struct path *
  vfs: prefer ->dentry->d_sb to ->mnt->mnt_sb
  vfs: trim includes a bit
  switch mnt_namespace ->root to struct mount
  vfs: take /proc/*/mounts and friends to fs/proc_namespace.c
  vfs: opencode mntget() mnt_set_mountpoint()
  vfs: spread struct mount - remaining argument of next_mnt()
  vfs: move fsnotify junk to struct mount
  vfs: move mnt_devname
  vfs: move mnt_list to struct mount
  vfs: switch pnode.h macros to struct mount *
  ...
2012-01-08 12:19:57 -08:00
Linus Torvalds
7affca3537 Merge branch 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
* 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (73 commits)
  arm: fix up some samsung merge sysdev conversion problems
  firmware: Fix an oops on reading fw_priv->fw in sysfs loading file
  Drivers:hv: Fix a bug in vmbus_driver_unregister()
  driver core: remove __must_check from device_create_file
  debugfs: add missing #ifdef HAS_IOMEM
  arm: time.h: remove device.h #include
  driver-core: remove sysdev.h usage.
  clockevents: remove sysdev.h
  arm: convert sysdev_class to a regular subsystem
  arm: leds: convert sysdev_class to a regular subsystem
  kobject: remove kset_find_obj_hinted()
  m86k: gpio - convert sysdev_class to a regular subsystem
  mips: txx9_sram - convert sysdev_class to a regular subsystem
  mips: 7segled - convert sysdev_class to a regular subsystem
  sh: dma - convert sysdev_class to a regular subsystem
  sh: intc - convert sysdev_class to a regular subsystem
  power: suspend - convert sysdev_class to a regular subsystem
  power: qe_ic - convert sysdev_class to a regular subsystem
  power: cmm - convert sysdev_class to a regular subsystem
  s390: time - convert sysdev_class to a regular subsystem
  ...

Fix up conflicts with 'struct sysdev' removal from various platform
drivers that got changed:
 - arch/arm/mach-exynos/cpu.c
 - arch/arm/mach-exynos/irq-eint.c
 - arch/arm/mach-s3c64xx/common.c
 - arch/arm/mach-s3c64xx/cpu.c
 - arch/arm/mach-s5p64x0/cpu.c
 - arch/arm/mach-s5pv210/common.c
 - arch/arm/plat-samsung/include/plat/cpu.h
 - arch/powerpc/kernel/sysfs.c
and fix up cpu_is_hotpluggable() as per Greg in include/linux/cpu.h
2012-01-07 12:03:30 -08:00
Arun Sharma
1ac9bc6943 sched/tracing: Add a new tracepoint for sleeptime
If CONFIG_SCHEDSTATS is defined, the kernel maintains
information about how long the task was sleeping or
in the case of iowait, blocking in the kernel before
getting woken up.

This will be useful for sleep time profiling.

Note: this information is only provided for sched_fair.
Other scheduling classes may choose to provide this in
the future.

Note: the delay includes the time spent on the runqueue
as well.

Signed-off-by: Arun Sharma <asharma@fb.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1324512940-32060-2-git-send-email-asharma@fb.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-23 17:56:17 +01:00
Dave Jones
664dfa65e8 sched: Disable scheduler warnings during oopses
The panic-on-framebuffer code seems to cause a schedule
to occur during an oops. This causes a bunch of extra
spew as can be seen in:

   https://bugzilla.redhat.com/attachment.cgi?id=549230

Don't do scheduler debug checks when we are oopsing already.

Signed-off-by: Dave Jones <davej@redhat.com>
Link: http://lkml.kernel.org/r/20111222213929.GA4722@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-23 11:20:50 +01:00
Daisuke Nishimura
62af3783e4 sched: Fix cgroup movement of waking process
There is a small race between try_to_wake_up() and sched_move_task(),
which is trying to move the process being woken up.

    try_to_wake_up() on CPU0       sched_move_task() on CPU1
--------------------------------+---------------------------------
  raw_spin_lock_irqsave(p->pi_lock)
  task_waking_fair()
    ->p.se.vruntime -= cfs_rq->min_vruntime
  ttwu_queue()
    ->send reschedule IPI to CPU1
  raw_spin_unlock_irqsave(p->pi_lock)
                                   task_rq_lock()
                                     -> tring to aquire both p->pi_lock and
                                        rq->lock with IRQ disabled
                                   task_move_group_fair()
                                     -> p.se.vruntime
                                          -= (old)cfs_rq->min_vruntime
                                          += (new)cfs_rq->min_vruntime
                                   task_rq_unlock()

                                   (via IPI)
                                   sched_ttwu_pending()
                                     raw_spin_lock(rq->lock)
                                     ttwu_do_activate()
                                       ...
                                       enqueue_entity()
                                         child.se->vruntime += cfs_rq->min_vruntime
                                     raw_spin_unlock(rq->lock)

As a result, vruntime of the process becomes far bigger than min_vruntime,
if (new)cfs_rq->min_vruntime >> (old)cfs_rq->min_vruntime.

This patch fixes this problem by just ignoring such process in
task_move_group_fair(), because the vruntime has already been normalized in
task_waking_fair().

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/20111215143741.df82dd50.nishimura@mxp.nes.nec.co.jp
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-21 10:34:52 +01:00
Daisuke Nishimura
7ceff013c4 sched: Fix cgroup movement of newly created process
There is a small race between do_fork() and sched_move_task(), which is
trying to move the child.

            do_fork()                 sched_move_task()
--------------------------------+---------------------------------
  copy_process()
    sched_fork()
      task_fork_fair()
        -> vruntime of the child is initialized
           based on that of the parent.
  -> we can see the child in "tasks" file now.
                                    task_rq_lock()
                                    task_move_group_fair()
                                      -> child.se.vruntime
                                           -= (old)cfs_rq->min_vruntime
                                           += (new)cfs_rq->min_vruntime
                                    task_rq_unlock()
  wake_up_new_task()
    ...
    enqueue_entity()
      child.se.vruntime += cfs_rq->min_vruntime

As a result, vruntime of the child becomes far bigger than min_vruntime,
if (new)cfs_rq->min_vruntime >> (old)cfs_rq->min_vruntime.

This patch fixes this problem by just ignoring such process in
task_move_group_fair(), because the vruntime has already been normalized in
task_fork_fair().

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/20111215143607.2ee12c5d.nishimura@mxp.nes.nec.co.jp
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-21 10:34:51 +01:00
Daisuke Nishimura
4fc420c91f sched: Fix cgroup movement of forking process
There is a small race between task_fork_fair() and sched_move_task(),
which is trying to move the parent.

        task_fork_fair()                 sched_move_task()
--------------------------------+---------------------------------
  cfs_rq = task_cfs_rq(current)
    -> cfs_rq is the "old" one.
  curr = cfs_rq->curr
    -> curr is set to the parent.
                                    task_rq_lock()
                                    dequeue_task()
                                      ->parent.se.vruntime -= (old)cfs_rq->min_vruntime
                                    enqueue_task()
                                      ->parent.se.vruntime += (new)cfs_rq->min_vruntime
                                    task_rq_unlock()
  raw_spin_lock_irqsave(rq->lock)
  se->vruntime = curr->vruntime
    -> vruntime of the child is set to that of the parent
       which has already been updated by sched_move_task().
  se->vruntime -= (old)cfs_rq->min_vruntime.
  raw_spin_unlock_irqrestore(rq->lock)

As a result, vruntime of the child becomes far bigger than expected,
if (new)cfs_rq->min_vruntime >> (old)cfs_rq->min_vruntime.

This patch fixes this problem by setting "cfs_rq" and "curr" after
holding the rq->lock.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/20111215143655.662676b0.nishimura@mxp.nes.nec.co.jp
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-21 10:34:49 +01:00
Kamalesh Babulal
11534ec5b6 sched: Remove cfs bandwidth period check in tg_set_cfs_period()
Remove cfs bandwidth period check from tg_set_cfs_period.
Invalid bandwidth period's lower/upper limits are denoted
by min_cfs_quota_period/max_cfs_quota_period repsectively,
and are checked against valid period in tg_set_cfs_bandwidth().

As pjt pointed out, negative input will result in very large unsigned
numbers and will be caught by the max allowed period test.

Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Acked-by: Paul Turner <pjt@google.com>
[ammended changelog to mention negative values]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111210135925.GA14593@linux.vnet.ibm.com
--
 kernel/sched/core.c |    3 ---
 1 file changed, 3 deletions(-)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-21 10:34:48 +01:00
Peter Zijlstra
a195f004e9 sched: Fix load-balance lock-breaking
The current lock break relies on contention on the rq locks, something
which might never come because we've got IRQs disabled. Or will be
very likely because on anything with more than 2 cpus a synchronized
load-balance pass will very likely cause contention on the rq locks.

Also the sched_nr_migrate thing fails when it gets trapped the loops
of either the cgroup muck in load_balance_fair() or the move_tasks()
load condition.

Instead, use the new lb_flags field to propagate break/abort
conditions for all these loops and create a new loop outside the irq
disabled on the break being required.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-tsceb6w61q0gakmsccix6xxi@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-21 10:34:47 +01:00
Peter Zijlstra
5b54b56be5 sched: Replace all_pinned with a generic flags field
Replace the all_pinned argument with a flags field so that we can add
some extra controls throughout that entire call chain.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-33kevm71m924ok1gpxd720v3@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-21 10:34:45 +01:00
Peter Zijlstra
518cd62341 sched: Only queue remote wakeups when crossing cache boundaries
Mike reported a 13% drop in netperf TCP_RR performance due to the
new remote wakeup code. Suresh too noticed some performance issues
with it.

Reducing the IPIs to only cross cache domains solves the observed
performance issues.

Reported-by: Suresh Siddha <suresh.b.siddha@intel.com>
Reported-by: Mike Galbraith <efault@gmx.de>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Kleikamp <dave.kleikamp@oracle.com>
Link: http://lkml.kernel.org/r/1323338531.17673.7.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-21 10:34:44 +01:00
Martin Schwidefsky
612ef28a04 Merge branch 'sched/core' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into cputime-tip
Conflicts:
	drivers/cpufreq/cpufreq_conservative.c
	drivers/cpufreq/cpufreq_ondemand.c
	drivers/macintosh/rack-meter.c
	fs/proc/stat.c
	fs/proc/uptime.c
	kernel/sched/core.c
2011-12-19 19:23:15 +01:00
Kees Cook
07cde2608a sched: Add missing rcu_dereference() around ->real_parent usage
Wrap another ->real_parent dereference while under rcu_read_lock.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Link: http://lkml.kernel.org/r/20111215164918.GA13003@www.outflux.net
[ tidied up the changelog ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-16 09:42:09 +01:00
Peter Zijlstra
067491b731 sched, nohz: Fix missing RCU read lock
Yong Zhang reported:

 > [ INFO: suspicious RCU usage. ]
 > kernel/sched/fair.c:5091 suspicious rcu_dereference_check() usage!

This is due to the sched_domain stuff being RCU protected and
commit 0b005cf5 ("sched, nohz: Implement sched group, domain
aware nohz idle load balancing") overlooking this fact.

The sd variable only lives inside the for_each_domain() block,
so we only need to wrap that.

Reported-by: Yong Zhang <yong.zhang0@gmail.com>
Tested-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1323264728.32012.107.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-08 05:45:48 +01:00
Suresh Siddha
cd490c5b28 sched, nohz: Set the NOHZ_BALANCE_KICK flag for idle load balancer
Intention is to set the NOHZ_BALANCE_KICK flag for the 'ilb_cpu'. Not
for the 'cpu' which is the local cpu. Fix the typo.

Reported-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1323199594.1984.18.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 20:51:29 +01:00
Suresh Siddha
8a6d42d1b3 sched, nohz: Fix the idle cpu check in nohz_idle_balance
cpu bit in the nohz.idle_cpu_mask are reset in the first busy tick after
exiting idle. So during nohz_idle_balance(), intention is to double
check if the cpu that is part of the idle_cpu_mask is indeed idle before
going ahead in performing idle balance for that cpu.

Fix the cpu typo in the idle_cpu() check during nohz_idle_balance().

Reported-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1323199177.1984.12.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 20:51:27 +01:00
Peter Zijlstra
f8b6d1cc7d sched: Use jump_labels for sched_feat
Now that we initialize jump_labels before sched_init() we can use them
for the debug features without having to worry about a window where
they have the wrong setting.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-vpreo4hal9e0kzqmg5y0io2k@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 20:51:26 +01:00
Glauber Costa
be726ffd1e sched/accounting: Fix parameter passing in task_group_account_field
The order of parameters is inverted. The index parameter
should come first.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1322863119-14225-3-git-send-email-glommer@parallels.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 20:51:24 +01:00
Glauber Costa
1c77f38ad6 sched/accounting: Fix user/system tick double accounting
Now that we're  pointing cpuacct's root cgroup to cpustat and accounting
through task_group_account_field(), we should not access cpustat directly.
Since it is done anyway inside the acessor function, we end up accounting
it twice, which is wrong.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1322863119-14225-2-git-send-email-glommer@parallels.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 20:51:23 +01:00
Glauber Costa
54c707e98d sched/accounting: Re-use scheduler statistics for the root cgroup
Right now, after we collect tick statistics for user and system and store them
in a well known location, we keep the same statistics again for cpuacct.
Since cpuacct is hierarchical, the numbers for the root cgroup should be
absolutely equal to the system-wide numbers.

So it would be better to just use it: this patch changes cpuacct accounting
in a way that the cpustat statistics are kept in a struct kernel_cpustat percpu
array. In the root cgroup case, we just point it to the main array. The rest of
the hierarchy walk can be totally disabled later with a static branch - but I am
not doing it here.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Tuner <pjt@google.com>
Link: http://lkml.kernel.org/r/1322498719-2255-4-git-send-email-glommer@parallels.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 20:51:21 +01:00
Mike Galbraith
b39e66eaf9 sched: Save some hrtick_start_fair cycles
hrtick_start_fair() shows up in profiles even when disabled.

v3.0.6

taskset -c 3 pipe-test

   PerfTop:     997 irqs/sec  kernel:89.5%  exact:  0.0% [1000Hz cycles],  (all, CPU: 3)
------------------------------------------------------------------------------------------------

             Virgin                                    Patched
             samples  pcnt function                    samples  pcnt function
             _______ _____ ___________________________ _______ _____ ___________________________

             2880.00 10.2% __schedule                  3136.00 11.3% __schedule
             1634.00  5.8% pipe_read                   1615.00  5.8% pipe_read
             1458.00  5.2% system_call                 1534.00  5.5% system_call
             1382.00  4.9% _raw_spin_lock_irqsave      1412.00  5.1% _raw_spin_lock_irqsave
             1202.00  4.3% pipe_write                  1255.00  4.5% copy_user_generic_string
             1164.00  4.1% copy_user_generic_string    1241.00  4.5% __switch_to
             1097.00  3.9% __switch_to                  929.00  3.3% mutex_lock
              872.00  3.1% mutex_lock                   846.00  3.0% mutex_unlock
              687.00  2.4% mutex_unlock                 804.00  2.9% pipe_write
              682.00  2.4% native_sched_clock           713.00  2.6% native_sched_clock
              643.00  2.3% system_call_after_swapgs     653.00  2.3% _raw_spin_unlock_irqrestore
              617.00  2.2% sched_clock_local            633.00  2.3% fsnotify
              612.00  2.2% fsnotify                     605.00  2.2% sched_clock_local
              596.00  2.1% _raw_spin_unlock_irqrestore  593.00  2.1% system_call_after_swapgs
              542.00  1.9% sysret_check                 559.00  2.0% sysret_check
              467.00  1.7% fget_light                   472.00  1.7% fget_light
              462.00  1.6% finish_task_switch           461.00  1.7% finish_task_switch
              437.00  1.5% vfs_write                    442.00  1.6% vfs_write
              431.00  1.5% do_sync_write                428.00  1.5% do_sync_write
              413.00  1.5% select_task_rq_fair          404.00  1.5% _raw_spin_lock_irq
              386.00  1.4% update_curr                  402.00  1.4% update_curr
              385.00  1.4% rw_verify_area               389.00  1.4% do_sync_read
              377.00  1.3% _raw_spin_lock_irq           378.00  1.4% vfs_read
              369.00  1.3% do_sync_read                 340.00  1.2% pipe_iov_copy_from_user
              360.00  1.3% vfs_read                     316.00  1.1% __wake_up_sync_key
*             342.00  1.2% hrtick_start_fair            313.00  1.1% __wake_up_common

Signed-off-by: Mike Galbraith <efault@gmx.de>
[ fixed !CONFIG_SCHED_HRTICK borkage ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1321971607.6855.17.camel@marge.simson.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 20:51:20 +01:00
Glauber Costa
44252e421a sched/accounting, cgroups: Reuse cgroup's parent pointer
We already have a pointer to the cgroup parent (whose data is more likely
to be in the cache than this, anyway), so there is no need to have this one
in cpuacct.

This patch makes the underlying cgroup be used instead.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Tuner <pjt@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1322498719-2255-3-git-send-email-glommer@parallels.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 09:06:40 +01:00
Glauber Costa
3292beb340 sched/accounting: Change cpustat fields to an array
This patch changes fields in cpustat from a structure, to an
u64 array. Math gets easier, and the code is more flexible.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Tuner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1322498719-2255-2-git-send-email-glommer@parallels.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 09:06:38 +01:00
Suresh Siddha
786d6dc7ae sched, nohz: Clean up the find_new_ilb() using sched groups nr_busy_cpus
nr_busy_cpus in the sched_group_power indicates whether the group
is semi idle or not. This helps remove the is_semi_idle_group() and simplify
the find_new_ilb() in the context of finding an optimal cpu that can do
idle load balancing.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.656983582@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 09:06:36 +01:00
Suresh Siddha
0b005cf54e sched, nohz: Implement sched group, domain aware nohz idle load balancing
When there are many logical cpu's that enter and exit idle often, members of
the global nohz data structure are getting modified very frequently causing
lot of cache-line contention.

Make the nohz idle load balancing more scalabale by using the sched domain
topology and 'nr_busy_cpu's in the struct sched_group_power.

Idle load balance is kicked on one of the idle cpu's when there is atleast
one idle cpu and:

 - a busy rq having more than one task or

 - a busy rq's scheduler group that share package resources (like HT/MC
   siblings) and has more than one member in that group busy or

 - for the SD_ASYM_PACKING domain, if the lower numbered cpu's in that
   domain are idle compared to the busy ones.

This will help in kicking the idle load balancing request only when
there is a potential imbalance. And once it is mostly balanced, these kicks will
be minimized.

These changes helped improve the workload that is context switch intensive
between number of task pairs by 2x on a 8 socket NHM-EX based system.

Reported-by: Tim Chen <tim.c.chen@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 09:06:34 +01:00
Suresh Siddha
69e1e811dc sched, nohz: Track nr_busy_cpus in the sched_group_power
Introduce nr_busy_cpus in the struct sched_group_power [Not in sched_group
because sched groups are duplicated for the SD_OVERLAP scheduler domain]
and for each cpu that enters and exits idle, this parameter will
be updated in each scheduler group of the scheduler domain that this cpu
belongs to.

To avoid the frequent update of this state as the cpu enters
and exits idle, the update of the stat during idle exit is
delayed to the first timer tick that happens after the cpu becomes busy.
This is done using NOHZ_IDLE flag in the struct rq's nohz_flags.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.555984323@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 09:06:32 +01:00
Suresh Siddha
1c792db7f7 sched, nohz: Introduce nohz_flags in 'struct rq'
Introduce nohz_flags in the struct rq, which will track these two flags
for now.

NOHZ_TICK_STOPPED keeps track of the tick stopped status that gets set when
the tick is stopped. It will be used to update the nohz idle load balancer data
structures during the first busy tick after the tick is restarted. At this
first busy tick after tickless idle, NOHZ_TICK_STOPPED flag will be reset.
This will minimize the nohz idle load balancer status updates that currently
happen for every tickless exit, making it more scalable when there
are many logical cpu's that enter and exit idle often.

NOHZ_BALANCE_KICK will track the need for nohz idle load balance
on this rq. This will replace the nohz_balance_kick in the rq, which was
not being updated atomically.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.499438999@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 09:06:30 +01:00
Shan Hai
5b680fd613 sched/rt: Code cleanup, remove a redundant function call
The second call to sched_rt_period() is redundant, because the value of the
rt_runtime was already read and it was protected by the ->rt_runtime_lock.

Signed-off-by: Shan Hai <haishan.bai@gmail.com>
Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1322535836-13590-2-git-send-email-haishan.bai@gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 09:06:28 +01:00
Suresh Siddha
4d78a2239e sched: Fix the sched group node allocation for SD_OVERLAP domains
For the SD_OVERLAP domain, sched_groups for each CPU's sched_domain are
privately allocated and not shared with any other cpu. So the
sched group allocation should come from the cpu's node for which
SD_OVERLAP sched domain is being setup.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111118230554.164910950@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 09:06:26 +01:00
Mike Galbraith
916671c08b sched: Set skip_clock_update in yield_task_fair()
This is another case where we are on our way to schedule(),
so can save a useless clock update and resulting microscopic
vruntime update.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1321971686.6855.18.camel@marge.simson.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 09:06:24 +01:00
Mike Galbraith
76854c7e8f sched: Use rt.nr_cpus_allowed to recover select_task_rq() cycles
rt.nr_cpus_allowed is always available, use it to bail from select_task_rq()
when only one cpu can be used, and saves some cycles for pinned tasks.

See the line marked with '*' below:

  # taskset -c 3 pipe-test

   PerfTop:     997 irqs/sec  kernel:89.5%  exact:  0.0% [1000Hz cycles],  (all, CPU: 3)
------------------------------------------------------------------------------------------------

             Virgin                                    Patched
             samples  pcnt function                    samples  pcnt function
             _______ _____ ___________________________ _______ _____ ___________________________

             2880.00 10.2% __schedule                  3136.00 11.3% __schedule
             1634.00  5.8% pipe_read                   1615.00  5.8% pipe_read
             1458.00  5.2% system_call                 1534.00  5.5% system_call
             1382.00  4.9% _raw_spin_lock_irqsave      1412.00  5.1% _raw_spin_lock_irqsave
             1202.00  4.3% pipe_write                  1255.00  4.5% copy_user_generic_string
             1164.00  4.1% copy_user_generic_string    1241.00  4.5% __switch_to
             1097.00  3.9% __switch_to                  929.00  3.3% mutex_lock
              872.00  3.1% mutex_lock                   846.00  3.0% mutex_unlock
              687.00  2.4% mutex_unlock                 804.00  2.9% pipe_write
              682.00  2.4% native_sched_clock           713.00  2.6% native_sched_clock
              643.00  2.3% system_call_after_swapgs     653.00  2.3% _raw_spin_unlock_irqrestore
              617.00  2.2% sched_clock_local            633.00  2.3% fsnotify
              612.00  2.2% fsnotify                     605.00  2.2% sched_clock_local
              596.00  2.1% _raw_spin_unlock_irqrestore  593.00  2.1% system_call_after_swapgs
              542.00  1.9% sysret_check                 559.00  2.0% sysret_check
              467.00  1.7% fget_light                   472.00  1.7% fget_light
              462.00  1.6% finish_task_switch           461.00  1.7% finish_task_switch
              437.00  1.5% vfs_write                    442.00  1.6% vfs_write
              431.00  1.5% do_sync_write                428.00  1.5% do_sync_write
*             413.00  1.5% select_task_rq_fair          404.00  1.5% _raw_spin_lock_irq
              386.00  1.4% update_curr                  402.00  1.4% update_curr
              385.00  1.4% rw_verify_area               389.00  1.4% do_sync_read
              377.00  1.3% _raw_spin_lock_irq           378.00  1.4% vfs_read
              369.00  1.3% do_sync_read                 340.00  1.2% pipe_iov_copy_from_user
              360.00  1.3% vfs_read                     316.00  1.1% __wake_up_sync_key
              342.00  1.2% hrtick_start_fair            313.00  1.1% __wake_up_common

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1321971504.6855.15.camel@marge.simson.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 08:51:26 +01:00
Suresh Siddha
77e81365e0 sched: Clean up domain traversal in select_idle_sibling()
Instead of going through the scheduler domain hierarchy multiple times
(for giving priority to an idle core over an idle SMT sibling in a busy
core), start with the highest scheduler domain with the SD_SHARE_PKG_RESOURCES
flag and traverse the domain hierarchy down till we find an idle group.

This cleanup also addresses an issue reported by Mike where the recent
changes returned the busy thread even in the presence of an idle SMT
sibling in single socket platforms.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1321556904.15339.25.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 08:51:25 +01:00
Andrew Vagin
b781a602ac events, sched: Add tracepoint for accounting blocked time
This tracepoint shows how long a task is sleeping in uninterruptible state.

E.g. it may show how long and where a mutex is waited for.

Signed-off-by: Andrew Vagin <avagin@openvz.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1322471015-107825-8-git-send-email-avagin@openvz.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06 08:51:23 +01:00
Peter Zijlstra
391e43da79 sched: Move all scheduler bits into kernel/sched/
There's too many sched*.[ch] files in kernel/, give them their own
directory.

(No code changed, other than Makefile glue added.)

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-11-17 12:20:22 +01:00