CPUs can go offline shortly after kfree_call_rcu() has been invoked,
which can leave memory stranded until those CPUs come back online.
This commit therefore drains the kcrp of each CPU, not just the
ones that happen to be online.
Acked-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcu_segcblist_accelerate() function returns true iff it is necessary
to request another grace period. A tracing session showed that this
function unnecessarily requests grace periods.
For example, consider the following sequence of events:
1. Callbacks are queued only on the NEXT segment of CPU A's callback list.
2. CPU A runs RCU_SOFTIRQ, accelerating these callbacks from NEXT to WAIT.
3. Thus rcu_segcblist_accelerate() returns true, requesting grace period N.
4. RCU's grace-period kthread wakes up on CPU B and starts grace period N.
4. CPU A notices the new grace period and invokes RCU_SOFTIRQ.
5. CPU A's RCU_SOFTIRQ again invokes rcu_segcblist_accelerate(), but
there are no new callbacks. However, rcu_segcblist_accelerate()
nevertheless (uselessly) requests a new grace period N+1.
This extra grace period results in additional lock contention and also
additional wakeups, all for no good reason.
This commit therefore adds a check to rcu_segcblist_accelerate() that
prevents the return of true when there are no new callbacks.
This change reduces the number of grace periods (GPs) and wakeups in each
of eleven five-second rcutorture runs as follows:
+----+-------------------+-------------------+
| # | Number of GPs | Number of Wakeups |
+====+=========+=========+=========+=========+
| 1 | With | Without | With | Without |
+----+---------+---------+---------+---------+
| 2 | 75 | 89 | 113 | 119 |
+----+---------+---------+---------+---------+
| 3 | 62 | 91 | 105 | 123 |
+----+---------+---------+---------+---------+
| 4 | 60 | 79 | 98 | 110 |
+----+---------+---------+---------+---------+
| 5 | 63 | 79 | 99 | 112 |
+----+---------+---------+---------+---------+
| 6 | 57 | 89 | 96 | 123 |
+----+---------+---------+---------+---------+
| 7 | 64 | 85 | 97 | 118 |
+----+---------+---------+---------+---------+
| 8 | 58 | 83 | 98 | 113 |
+----+---------+---------+---------+---------+
| 9 | 57 | 77 | 89 | 104 |
+----+---------+---------+---------+---------+
| 10 | 66 | 82 | 98 | 119 |
+----+---------+---------+---------+---------+
| 11 | 52 | 82 | 83 | 117 |
+----+---------+---------+---------+---------+
The reduction in the number of wakeups ranges from 5% to 40%.
Cc: urezki@gmail.com
[ paulmck: Rework commit log and comment. ]
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds an rcutorture.leakpointer module parameter that
intentionally leaks an RCU-protected pointer out of the RCU read-side
critical section and checks to see if the corresponding grace period
has elapsed, emitting a WARN_ON_ONCE() if so. This module parameter can
be used to test facilities like CONFIG_RCU_STRICT_GRACE_PERIOD that end
grace periods quickly.
While in the area, also document rcutorture.irqreader, which was
previously left out.
Reported-by Jann Horn <jannh@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, registering and unregistering the OOM notifier is done
right before and after the test, respectively. This will not work
well for multi-threaded tests, so this commit hoists this registering
and unregistering up into the rcu_torture_fwd_prog_init() and
rcu_torture_fwd_prog_cleanup() functions.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently in the unlikely event that buf fails to be allocated it
is dereferenced a few times. Use the errexit flag to determine if
buf should be written to to avoid the null pointer dereferences.
Addresses-Coverity: ("Dereference after null check")
Fixes: f518f154ec ("refperf: Dynamically allocate experiment-summary output buffer")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The current rcutorture forward-progress code assumes that it is the
only cause of out-of-memory (OOM) events. For script-based rcutorture
testing, this assumption is in fact correct. However, testing based
on modprobe/rmmod might well encounter external OOM events, which could
happen at any time.
This commit therefore properly synchronizes the interaction between
rcutorture's forward-progress testing and its OOM notifier by adding a
global mutex.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The conversion of rcu_fwds to dynamic allocation failed to actually
allocate the required structure. This commit therefore allocates it,
frees it, and updates rcu_fwds accordingly. While in the area, it
abstracts the cleanup actions into rcu_torture_fwd_prog_cleanup().
Fixes: 5155be9994 ("rcutorture: Dynamically allocate rcu_fwds structure")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds code to print the grace-period number at the start
of the test along with both the grace-period number and the number of
elapsed grace periods at the end of the test. Note that variants of
RCU)without the notion of a grace-period number (for example, Tiny RCU)
just print zeroes.
[ paulmck: Adjust commit log. ]
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
KCSAN is now in mainline, so this commit removes the stubs for the
data_race(), ASSERT_EXCLUSIVE_WRITER(), and ASSERT_EXCLUSIVE_ACCESS()
macros.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The x86/entry work removed all uses of __rcu_is_watching(), therefore
this commit removes it entirely.
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <x86@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The RCU grace-period kthread's force-quiescent state (FQS) loop should
never see an offline CPU that has not yet reported a quiescent state.
After all, the offline CPU should have reported a quiescent state
during the CPU-offline process, or, failing that, by rcu_gp_init()
if it ran concurrently with either the CPU going offline or the last
task on a leaf rcu_node structure exiting its RCU read-side critical
section while all CPUs corresponding to that structure are offline.
The FQS loop should therefore complain if it does see an offline CPU
that has not yet reported a quiescent state.
And it does, but only once the grace period has been in force for a
full second. This commit therefore makes this warning more aggressive,
so that it will trigger as soon as the condition makes its appearance.
Light testing with TREE03 and hotplug shows no warnings. This commit
also converts the warning to WARN_ON_ONCE() in order to stave off possible
log spam.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Since at least v4.19, the FQS loop no longer reports quiescent states
for offline CPUs except in emergency situations.
This commit therefore fixes the comment in rcu_gp_init() to match the
current code.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit increases RCU's ability to defend itself by emitting a warning
if one of the nocb CB kthreads invokes the GP kthread's wait function.
This warning augments a similar check that is carried out at the end
of rcutorture testing and when RCU CPU stall warnings are emitted.
The problem with those checks is that the miscreants have long since
departed and disposed of any and all evidence.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
When the rcu_cpu_started per-CPU variable was added by commit
f64c6013a2 ("rcu/x86: Provide early rcu_cpu_starting() callback"),
there were multiple sets of per-CPU rcu_data structures. Therefore, the
rcu_cpu_started flag was added as a separate per-CPU variable. But now
there is only one set of per-CPU rcu_data structures, so this commit
moves rcu_cpu_started to a new ->cpu_started field in that structure.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Given that sysfs can change the value of rcu_cpu_stall_ftrace_dump at any
time, this commit adds a READ_ONCE() to the accesses to that variable.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Given that sysfs can change the value of rcu_kick_kthreads at any time,
this commit adds a READ_ONCE() to the sole access to that variable.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Given that sysfs can change the value of rcu_resched_ns at any time,
this commit adds a READ_ONCE() to the sole access to that variable.
While in the area, this commit also adds bounds checking, clamping the
value to at least a millisecond, but no longer than a second.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Given that sysfs can change the value of rcu_divisor at any time, this
commit adds a READ_ONCE to the sole access to that variable. While in
the area, this commit also adds bounds checking, clamping the value to
a shift that makes sense for a signed long.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcu_data structure's ->nocb_timer field is used to defer wakeups of
the corresponding no-CBs CPU's grace-period kthread ("rcuog*"), and that
structure's ->nocb_defer_wakeup field is used to track such deferral.
This means that the show_rcu_nocb_state() printing an error when those
fields are set for a CPU not corresponding to a no-CBs grace-period
kthread is erroneous.
This commit therefore switches the check from ->nocb_timer to
->nocb_bypass_timer and removes the check of ->nocb_defer_wakeup.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Originally, the call to rcu_preempt_blocked_readers_cgp() from
force_qs_rnp() had to be conditioned on CONFIG_PREEMPT_RCU=y, as in
commit a77da14ce9 ("rcu: Yet another fix for preemption and CPU
hotplug"). However, there is now a CONFIG_PREEMPT_RCU=n definition of
rcu_preempt_blocked_readers_cgp() that unconditionally returns zero, so
invoking it is now safe. In addition, the CONFIG_PREEMPT_RCU=n definition
of rcu_initiate_boost() simply releases the rcu_node structure's ->lock,
which is what happens when the "if" condition evaluates to false.
This commit therefore drops the IS_ENABLED(CONFIG_PREEMPT_RCU) check,
so that rcu_initiate_boost() is called only in CONFIG_PREEMPT_RCU=y
kernels when there are readers blocking the current grace period.
This does not change the behavior, but reduces code-reader confusion by
eliminating non-CONFIG_PREEMPT_RCU=y calls to rcu_initiate_boost().
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
On callback overload, it is necessary to quickly detect idle CPUs,
and rcu_gp_fqs_check_wake() checks for this condition. Unfortunately,
the code following the call to this function does not repeat this check,
which means that in reality no actual quiescent-state forcing, instead
only a couple of quick and pointless wakeups at the beginning of the
grace period.
This commit therefore adds a check for the RCU_GP_FLAG_OVLD flag in
the post-wakeup "if" statement in rcu_gp_fqs_loop().
Fixes: 1fca4d12f4 ("rcu: Expedite first two FQS scans under callback-overload conditions")
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
A message of the form "rcu: !!! lDTs ." can be tracked down, but
doing so is not trivial. This commit therefore eases this process by
adding text so that this error message now reads as follows:
"rcu: nocb GP activity on CB-only CPU!!! lDTs ."
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
During acceleration of CB, the rsp's gp_seq is rcu_seq_snap'd. This is
the value used for acceleration - it is the value of gp_seq at which it
is safe the execute all callbacks in the callback list.
The rdp's gp_seq is not very useful for this scenario. Make
rcu_grace_period report the gp_seq_req instead as it allows one to
reason about how the acceleration works.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit moves the initialization of the CONFIG_PREEMPT=n version of
the rcu_exp_handler() function's rdp and rnp local variables into their
respective declarations to save a couple lines of code.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
KCSAN is now in mainline, so this commit removes the stubs for the
data_race(), ASSERT_EXCLUSIVE_WRITER(), and ASSERT_EXCLUSIVE_ACCESS()
macros.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
KCSAN is now in mainline, so this commit removes the stubs for the
data_race(), ASSERT_EXCLUSIVE_WRITER(), and ASSERT_EXCLUSIVE_ACCESS()
macros.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
KCSAN is now in mainline, so this commit removes the stubs for the
data_race(), ASSERT_EXCLUSIVE_WRITER(), and ASSERT_EXCLUSIVE_ACCESS()
macros.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Patch series "kasan: memorize and print call_rcu stack", v8.
This patchset improves KASAN reports by making them to have call_rcu()
call stack information. It is useful for programmers to solve
use-after-free or double-free memory issue.
The KASAN report was as follows(cleaned up slightly):
BUG: KASAN: use-after-free in kasan_rcu_reclaim+0x58/0x60
Freed by task 0:
kasan_save_stack+0x24/0x50
kasan_set_track+0x24/0x38
kasan_set_free_info+0x18/0x20
__kasan_slab_free+0x10c/0x170
kasan_slab_free+0x10/0x18
kfree+0x98/0x270
kasan_rcu_reclaim+0x1c/0x60
Last call_rcu():
kasan_save_stack+0x24/0x50
kasan_record_aux_stack+0xbc/0xd0
call_rcu+0x8c/0x580
kasan_rcu_uaf+0xf4/0xf8
Generic KASAN will record the last two call_rcu() call stacks and print up
to 2 call_rcu() call stacks in KASAN report. it is only suitable for
generic KASAN.
This feature considers the size of struct kasan_alloc_meta and
kasan_free_meta, we try to optimize the structure layout and size, lets it
get better memory consumption.
[1]https://bugzilla.kernel.org/show_bug.cgi?id=198437
[2]https://groups.google.com/forum/#!searchin/kasan-dev/better$20stack$20traces$20for$20rcu%7Csort:date/kasan-dev/KQsjT_88hDE/7rNUZprRBgAJ
This patch (of 4):
This feature will record the last two call_rcu() call stacks and prints up
to 2 call_rcu() call stacks in KASAN report.
When call_rcu() is called, we store the call_rcu() call stack into slub
alloc meta-data, so that the KASAN report can print rcu stack.
[1]https://bugzilla.kernel.org/show_bug.cgi?id=198437
[2]https://groups.google.com/forum/#!searchin/kasan-dev/better$20stack$20traces$20for$20rcu%7Csort:date/kasan-dev/KQsjT_88hDE/7rNUZprRBgAJ
[walter-zh.wu@mediatek.com: build fix]
Link: http://lkml.kernel.org/r/20200710162401.23816-1-walter-zh.wu@mediatek.com
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Link: http://lkml.kernel.org/r/20200710162123.23713-1-walter-zh.wu@mediatek.com
Link: http://lkml.kernel.org/r/20200601050847.1096-1-walter-zh.wu@mediatek.com
Link: http://lkml.kernel.org/r/20200601050927.1153-1-walter-zh.wu@mediatek.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
static priority level knowledge from non-scheduler code.
The three APIs for non-scheduler code to set SCHED_FIFO are:
- sched_set_fifo()
- sched_set_fifo_low()
- sched_set_normal()
These are two FIFO priority levels: default (high), and a 'low' priority level,
plus sched_set_normal() to set the policy back to non-SCHED_FIFO.
Since the changes affect a lot of non-scheduler code, we kept this in a separate
tree.
When merging to the latest upstream tree there's a conflict in drivers/spi/spi.c,
which can be resolved via:
sched_set_fifo(ctlr->kworker_task);
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-fifo-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull sched/fifo updates from Ingo Molnar:
"This adds the sched_set_fifo*() encapsulation APIs to remove static
priority level knowledge from non-scheduler code.
The three APIs for non-scheduler code to set SCHED_FIFO are:
- sched_set_fifo()
- sched_set_fifo_low()
- sched_set_normal()
These are two FIFO priority levels: default (high), and a 'low'
priority level, plus sched_set_normal() to set the policy back to
non-SCHED_FIFO.
Since the changes affect a lot of non-scheduler code, we kept this in
a separate tree"
* tag 'sched-fifo-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
sched,tracing: Convert to sched_set_fifo()
sched: Remove sched_set_*() return value
sched: Remove sched_setscheduler*() EXPORTs
sched,psi: Convert to sched_set_fifo_low()
sched,rcutorture: Convert to sched_set_fifo_low()
sched,rcuperf: Convert to sched_set_fifo_low()
sched,locktorture: Convert to sched_set_fifo()
sched,irq: Convert to sched_set_fifo()
sched,watchdog: Convert to sched_set_fifo()
sched,serial: Convert to sched_set_fifo()
sched,powerclamp: Convert to sched_set_fifo()
sched,ion: Convert to sched_set_normal()
sched,powercap: Convert to sched_set_fifo*()
sched,spi: Convert to sched_set_fifo*()
sched,mmc: Convert to sched_set_fifo*()
sched,ivtv: Convert to sched_set_fifo*()
sched,drm/scheduler: Convert to sched_set_fifo*()
sched,msm: Convert to sched_set_fifo*()
sched,psci: Convert to sched_set_fifo*()
sched,drbd: Convert to sched_set_fifo*()
...
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Merge tag 'core-urgent-2020-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull rcu fixlet from Thomas Gleixner:
"A single fix for a printk format warning in RCU"
* tag 'core-urgent-2020-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rcuperf: Fix printk format warning
RCU is supposed to be watching all non-idle kernel code and also all
softirq handlers. This commit adds some teeth to this statement by
adding a WARN_ON_ONCE().
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Coccinelle reports a warning
WARNING: Assignment of 0/1 to bool variable
The root cause is that the variable lastphase is a bool, but is
initialised with integer 0. This commit therefore replaces the 0 with
a false.
Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, the rcu_torture_current variable remains non-NULL until after
all readers have stopped. During this time, rcu_torture_stats_print()
will think that the test is still ongoing, which can result in confusing
dmesg output. This commit therefore NULLs rcu_torture_current immediately
after the rcu_torture_writer() kthread has decided to stop, thus informing
rcu_torture_stats_print() much sooner.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Several variants of Linux-kernel RCU interact with task-exit processing,
including preemptible RCU, Tasks RCU, and Tasks Trace RCU. This commit
therefore adds testing of this interaction to rcutorture by adding
rcutorture.read_exit_burst and rcutorture.read_exit_delay kernel-boot
parameters. These kernel parameters control the frequency and spacing
of special read-then-exit kthreads that are spawned.
[ paulmck: Apply feedback from Dan Carpenter's static checker. ]
[ paulmck: Reduce latency to avoid false-positive shutdown hangs. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
SRCU disables interrupts to get a stable per-CPU pointer and then
acquires the spinlock which is in the per-CPU data structure. The
release uses spin_unlock_irqrestore(). While this is correct on a non-RT
kernel, this conflicts with the RT semantics because the spinlock is
converted to a 'sleeping' spinlock. Sleeping locks can obviously not be
acquired with interrupts disabled.
Acquire the per-CPU pointer `ssp->sda' without disabling preemption and
then acquire the spinlock_t of the per-CPU data structure. The lock will
ensure that the data is consistent.
The added call to check_init_srcu_struct() is now needed because a
statically defined srcu_struct may remain uninitialized until this
point and the newly introduced locking operation requires an initialized
spinlock_t.
This change was tested for four hours with 8*SRCU-N and 8*SRCU-P without
causing any warnings.
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: rcu@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit further avoids conflation of refperf with the kernel's perf
feature by renaming kernel/rcu/refperf.c to kernel/rcu/refscale.c,
and also by similarly renaming the functions and variables inside
this file. This has the side effect of changing the names of the
kernel boot parameters, so kernel-parameters.txt and ver_functions.sh
are also updated.
The rcutorture --torture type remains refperf, and this will be
addressed in a separate commit.
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The old Kconfig option name is all too easy to conflate with the
unrelated "perf" feature, so this commit renames RCU_REF_PERF_TEST to
RCU_REF_SCALE_TEST.
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The synchronize_rcu_tasks_trace() header comment incorrectly claims that
any number of things delimit RCU Tasks Trace read-side critical sections,
when in fact only rcu_read_lock_trace() and rcu_read_unlock_trace() do so.
This commit therefore fixes this comment, and, while in the area, fixes
a typo in the rcu_read_lock_trace() header comment.
Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds testing for RCU Tasks readers to the refperf module.
This also applies to RCU Rude readers, as both flavors have empty
(as in non-existent) read-side markers.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The current units of microseconds are too coarse, so this commit
changes the units to nanoseconds. However, ndelay is used only for the
nanoseconds with udelay being used for whole microseconds. For example,
setting refperf.readdelay=1500 results in a udelay(1) followed by an
ndelay(500).
Suggested-by: Akira Yokosawa <akiyks@gmail.com>
[ paulmck: Abstracted delay per Akira feedback and move from 80 to 100 lines. ]
[ paulmck: Fix names as suggested by kbuild test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
A 64-bit division was introduced in refperf, breaking compilation
on all 32-bit architectures:
kernel/rcu/refperf.o: in function `main_func':
refperf.c:(.text+0x57c): undefined reference to `__aeabi_uldivmod'
Fix this by using div_u64 to mark the expensive operation.
[ paulmck: Update primitive and format per Nathan Chancellor. ]
Fixes: bd5b16d6c88d ("refperf: Allow decimal nanoseconds")
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Valdis Klētnieks <valdis.kletnieks@vt.edu>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
With the various measurement optimizations, 10,000 loops normally
suffices. This commit therefore reduces the refperf.loops default value
from 10,000,000 to 10,000.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a refperf.readdelay module parameter that controls the
duration of each critical section. This parameter allows gathering data
showing how the performance differences between the various primitives
vary with critical-section length.
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit moves the reader-launch wait loop from ref_perf_init()
to main_func(), removing one layer of wakeup and allowing slightly
faster system boot.
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The experiment-number column is currently labeled "Threads", which is
misleading at best. This commit therefore relabels it as "Runs", and
adjusts the scripts accordingly.
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
