It is possible that the rcuperf kernel test runs concurrently with init
starting up. During this time, the system is running all grace periods
as expedited. However, rcuperf can also be run for normal GP tests.
Right now, it depends on a holdoff time before starting the test to
ensure grace periods start later. This works fine with the default
holdoff time however it is not robust in situations where init takes
greater than the holdoff time to finish running. Or, as in my case:
I modified the rcuperf test locally to also run a thread that did
preempt disable/enable in a loop. This had the effect of slowing down
init. The end result was that the "batches:" counter in rcuperf was 0
causing a division by 0 error in the results. This counter was 0 because
only expedited GPs seem to happen, not normal ones which led to the
rcu_state.gp_seq counter remaining constant across grace periods which
unexpectedly happen to be expedited. The system was running expedited
RCU all the time because rcu_unexpedited_gp() would not have run yet
from init. In other words, the test would concurrently with init
booting in expedited GP mode.
To fix this properly, this commit waits until system_state is set to
SYSTEM_RUNNING before starting the test. This change is made just
before kernel_init() invokes rcu_end_inkernel_boot(), and this latter
is what turns off boot-time expediting of RCU grace periods.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
The rcu_bh rcuperf type was removed by commit 620d246065cd("rcuperf:
Remove the "rcu_bh" and "sched" torture types"), but it lives on in the
MODULE_PARM_DESC() of perf_type. This commit therefore changes that
module-parameter description to substitute srcu for rcu_bh.
Signed-off-by: Xiao Yang <ice_yangxiao@163.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
If the specified rcuperf.perf_type is not in the rcu_perf_init()
function's perf_ops[] array, rcuperf prints some console messages and
then invokes rcu_perf_cleanup() to set state so that a future torture
test can run. However, rcu_perf_cleanup() also attempts to end the
test that didn't actually start, and in doing so relies on the value
of cur_ops, a value that is not particularly relevant in this case.
This can result in confusing output or even follow-on failures due to
attempts to use facilities that have not been properly initialized.
This commit therefore sets the value of cur_ops to NULL in this case and
inserts a check near the beginning of rcu_perf_cleanup(), thus avoiding
relying on an irrelevant cur_ops value.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
The ever-evolving IS_ENABLED() macro is intended for CONFIG_* Kconfig
options, but rcuperf currently uses it for the decidedly non-CONFIG_*
MODULE macro. In the spirit of not inviting trouble, this commit
substitutes tried-and-true #ifdef.
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Now that the RCU-bh and RCU-sched update-side functions are simple
wrappers around their RCU counterparts, there isn't a whole lot of point
in testing them. This commit therefore removes the "rcu_bh" and "sched"
torture types from rcuperf.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
When running a built-in rcuperf test, specifying an invalid perf type
results in what looks like a hard hang, with the error messages hidden
by other boot-time output. This commit therefore executes a WARN_ON()
in this case so that the splat appears just following the error messages.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This function is in rcuperf.c, which is not an include file, so there
is no problem dropping the "inline", especially given that this function
is invoked only twice per rcuperf run. This commit therefore delegates
the inlining decision to the compiler by dropping the "inline".
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit also adjusts some whitespace while in the area.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Revert string-breaking %s as requested by Andy Shevchenko. ]
The new ->gq_seq grace-period sequence numbers must be shifted down,
which give artifacts when these numbers wrap. This commit therefore
enables rcutorture and rcuperf to handle grace-period sequence numbers
even if they do wrap. It does this by allowing a special subtraction
function to be specified, and this function subtracts before shifting.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The rcutorture test invokes rcu_batches_started(),
rcu_batches_completed(), rcu_batches_started_bh(),
rcu_batches_completed_bh(), rcu_batches_started_sched(), and
rcu_batches_completed_sched() to do grace-period consistency checks,
and rcuperf uses the _completed variants for statistics.
These functions use ->gpnum and ->completed. This commit therefore
replaces them with rcu_get_gp_seq(), rcu_bh_get_gp_seq(), and
rcu_sched_get_gp_seq(), adjusting rcutorture and rcuperf to make
use of them.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit adds "#define pr_fmt(fmt) fmt" to the torture-test files
in order to keep the current dmesg format. Once Joe's commits have
hit mainline, these definitions will be changed in order to automatically
generate the dmesg line prefix that the scripts expect. This will have
the beneficial side-effect of allowing printk() formats to be used more
widely and of shortening some pr_*() lines.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Joe Perches <joe@perches.com>
Some bugs reproduce quickly only at high CPU-hotplug rates, so the
rcutorture TREE03 scenario now has only 200 milliseconds spacing between
CPU-hotplug operations. At this rate, the torture-test pair of console
messages per operation becomes a bit voluminous. This commit therefore
converts the torture-test set of "verbose" kernel-boot arguments from
bool to int, and prints the extra console messages only when verbose=2.
The default is still verbose=1.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Commit e31d28b6ab ("trace: Eliminate cond_resched_rcu_qs() in favor
of cond_resched()") substituted cond_resched() for the earlier call
to cond_resched_rcu_qs(). However, the new-age cond_resched() does
not do anything to help RCU-tasks grace periods because (1) RCU-tasks
is only enabled when CONFIG_PREEMPT=y and (2) cond_resched() is a
complete no-op when preemption is enabled. This situation results
in hangs when running the trace benchmarks.
A number of potential fixes were discussed on LKML
(https://lkml.kernel.org/r/20180224151240.0d63a059@vmware.local.home),
including making cond_resched() not be a no-op; making cond_resched()
not be a no-op, but only when running tracing benchmarks; reverting
the aforementioned commit (which works because cond_resched_rcu_qs()
does provide an RCU-tasks quiescent state; and adding a call to the
scheduler/RCU rcu_note_voluntary_context_switch() function. All were
deemed unsatisfactory, either due to added cond_resched() overhead or
due to magic functions inviting cargo culting.
This commit renames cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs(),
which provides a clear hint as to what this function is doing and
why and where it should be used, and then replaces the call to
cond_resched() with cond_resched_tasks_rcu_qs() in the trace benchmark's
benchmark_event_kthread() function.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
The default values for nreader and nwriter are apparently not all that
user-friendly, resulting in people doing scalability tests that ran all
runs at large scale. This commit therefore makes both the nreaders and
nwriters module default to the number of CPUs, and adds a comment to
rcuperf.c stating that the number of CPUs should be specified using the
nr_cpus kernel boot parameter. This commit also eliminates the redundant
rcuperf scripting specification of default values for these parameters.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The purpose of torture_runnable is to allow rcutorture and locktorture
to be started and stopped via sysfs when they are built into the kernel
(as in not compiled as loadable modules). However, the 0444 permissions
for both instances of torture_runnable prevent this use case from ever
being put into practice. Given that there have been no complaints
about this deficiency, it is reasonable to conclude that no one actually
makes use of this sysfs capability. The perf_runnable module parameter
for rcuperf is in the same situation.
This commit therefore removes both torture_runnable instances as well
as perf_runnable.
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The synchronize_rcu_tasks() and call_rcu_tasks() APIs are now available
regardless of kernel configuration, so this commit removes the
CONFIG_TASKS_RCU ifdef from rcuperf.c.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The rcu_gp_is_normal(), rcu_gp_is_expedited(), rcu_expedite_gp(), and
rcu_unexpedite_gp() functions are intended only for use within the
RCU implementation itself -- the sysfs access is what should be used
outside of RCU. This commit therefore moves the declarations for
these functions to kernel/rcu/rcu.h, and also includes this file into
kernel/rcu/rcutorture.c and kernel/rcu/rcuperf.c. This also has the
beneficial effect of shrinking rcupdate.c a bit.
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit adds a writer_holdoff boot parameter to rcuperf, which is
intended to be used to test Tree SRCU's auto-expediting. This
boot parameter is in microseconds, and defaults to zero (that is,
disabled). Set it to a bit larger than srcutree.exp_holdoff,
keeping the nanosecond/microsecond conversion, to force Tree SRCU
to auto-expedite more aggressively.
This commit also adds documentation for this parameter, and fixes some
alphabetization while in the neighborhood.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Common-case use of rcuperf must set rcuperf.nreaders=0 and if not built
as a module, rcuperf.shutdown. This commit therefore sets the default
for rcuperf.nreaders to zero and sets the default for rcuperf.shutdown
to zero if rcuperf is built as a module and to one otherwise.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit adds a perf_type of "srcud", which species that rcuperf
test SRCU on a dynamically initialized srcu_struct.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit upgrades rcuperf so that it can do performance testing on
asynchronous grace-period primitives such as call_srcu(). There is
a new rcuperf.gp_async module parameter that specifies this new behavior,
with the pre-existing rcuperf.gp_exp testing expedited grace periods such as
synchronize_rcu_expedited, and with the default being to test synchronous
non-expedited grace periods such as synchronize_rcu().
There is also a new rcuperf.gp_async_max module parameter that specifies
the maximum number of outstanding callbacks per writer kthread, defaulting
to 1,000. When this limit is exceeded, the writer thread invokes the
appropriate flavor of rcu_barrier() to wait for callbacks to drain.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Removed the redundant initialization noted by Arnd Bergmann. ]
Current rcuperf startup checks to see if the user asked to measure
only expedited grace periods, yet constrained all grace periods to be
normal, or if the user asked to measure only normal grace periods, yet
constrained all grace periods to be expedited. Useless tests of this
sort are aborted.
Unfortunately, making RCU work through the mid-boot dead zone [1] puts
RCU into expedited-only mode during that zone. Which happens to also
be the exact time that rcuperf carries out the aforementioned check.
So if the user asks rcuperf to measure only normal grace periods (the
default), rcuperf will now always complain and terminate the test.
This commit therefore moves the checks to rcu_perf_cleanup(). This has
the disadvantage of failing to abort useless tests, but avoids the need to
create yet another kthread and the need to do fiddly checks involving the
holdoff time. (Yes, another approach is to do the checks in a late-stage
init function, but that would require some way to communicate badness
to rcuperf's kthreads, and seems not worth the bother.)
[1] https://lwn.net/Articles/716148/
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
We are going to move scheduler ABI details to <uapi/linux/sched/types.h>,
which will be used from a number of .c files.
Create empty placeholder header that maps to <linux/types.h>.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
A few rcuperf dmesg output messages have no space between the flag and
the start of the message. In contrast, every other messages consistently
supplies a single space. This difference makes rcuperf dmesg output
hard to read and to mechanically parse. This commit therefore fixes
this problem by modifying a pr_alert() call and PERFOUT_STRING() macro
function to provide that single space.
Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Fix to return a negative error code -ENOMEM from kcalloc() error
handling case instead of 0, as done elsewhere in this function.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
0day found a boot warning triggered in rcu_perf_writer() on !SMP kernel:
WARN_ON(rcu_gp_is_normal() && gp_exp);
, the root cause of which is trying to measure expedited grace
periods(by setting gp_exp to true by default) when all the grace periods
are normal(TINY RCU only has normal grace periods).
However, such a mis-setting would only result in failing to measure the
performance for a specific kind of grace periods, therefore using a
WARN_ON to check this is a little overkilling. We could handle this
inside rcuperf module via some error messages to tell users about the
mis-settings.
Therefore this patch removes the WARN_ON in rcu_perf_writer() and
handles those checkings in rcu_perf_init() with plain if() code.
Moreover, this patch changes the default value of gp_exp to 1) align
with rcutorture tests and 2) make the default setting work for all RCU
implementations by default.
Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Fixes: http://lkml.kernel.org/r/57411b10.mFvG0+AgcrMXGtcj%fengguang.wu@intel.com
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit applies the infamous IS_ENABLED() macro to eliminate a #ifdef.
It also eliminates the RCU_PERF_TEST_RUNNABLE Kconfig option in favor
of the already-existing rcuperf.perf_runnable kernel boot parameter.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
After finishing its tests rcuperf tries to wake up shutdown_wq even if
"shutdown" param is set to false, resulting in a wake_up() call on an
unitialized wait_queue_head_t which leads to "BUG: spinlock bad magic" and
"BUG: unable to handle kernel NULL pointer dereference".
Fix by checking "shutdown" param before waking up the queue.
Signed-off-by: Artem Savkov <artem.savkov@gmail.com>
Running rcuperf can result in RCU CPU stall warnings and RT throttling.
These occur because on of the real-time writer processes does
ftrace_dump() while still running at real-time priority. This commit
therefore prevents these problems by setting the writer thread back to
SCHED_NORMAL (AKA SCHED_OTHER) before doing ftrace_dump().
In addition, this commit adds a small fixed delay before dumping ftrace
buffer in order to decrease the probability that this dumping will
interfere with other writers' grace periods.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Boot-time activity can legitimately grab CPUs for extended time periods,
so the commit adds a boot parameter to delay the start of the performance
test until boot has completed. Defaults to 10 seconds.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit enables ftrace in the rcuperf TREE kernel build and adds
an ftrace_dump() at the end of rcuperf processing. This data will be
used to measure the actual durations of the expedited grace periods
without the added delays inherent in the kernel-module measurements.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit forces more deterministic update-side behavior by setting
rcuperf's rcu_perf_writer() kthreads to real-time priority.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit forces more deterministic behavior by binding rcuperf's
rcu_perf_reader() and rcu_perf_writer() kthreads to their respective
CPUs.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit adds a new rcuperf module that carries out simple performance
tests of RCU grace periods.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
