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Commit df37e66b authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Add rcuperf holdoff boot parameter to reduce interference 



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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 2b03d038

Documentation/kernel-parameters.txt

+6 −0
Original line number Diff line number Diff line
@@ -3288,6 +3288,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			Measure performance of expedited synchronous

			grace-period primitives.



	rcuperf.holdoff= [KNL]

			Set test-start holdoff period.  The purpose of

			this parameter is to delay the start of the

			test until boot completes in order to avoid

			interference.



	rcuperf.nreaders= [KNL]

			Set number of RCU readers.  The value -1 selects

			N, where N is the number of CPUs.  A value

kernel/rcu/rcuperf.c

+5 −0
Original line number Diff line number Diff line
@@ -59,6 +59,7 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>"); 
	do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0)



torture_param(bool, gp_exp, true, "Use expedited GP wait primitives");

torture_param(int, holdoff, 10, "Holdoff time before test start (s)");

torture_param(int, nreaders, -1, "Number of RCU reader threads");

torture_param(int, nwriters, -1, "Number of RCU updater threads");

torture_param(bool, shutdown, false, "Shutdown at end of performance tests.");
@@ -368,6 +369,10 @@ rcu_perf_writer(void *arg) 
	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));

	sp.sched_priority = 1;

	sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);



	if (holdoff)

		schedule_timeout_uninterruptible(holdoff * HZ);



	t = ktime_get_mono_fast_ns();

	if (atomic_inc_return(&n_rcu_perf_writer_started) >= nrealwriters) {

		t_rcu_perf_writer_started = t;