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>
