From df37e66bfdbb57e8cae7dbf39a0c66b1b8701338 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 30 Jan 2016 20:56:38 -0800 Subject: [PATCH] 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: Paul E. McKenney --- Documentation/kernel-parameters.txt | 6 ++++++ kernel/rcu/rcuperf.c | 5 +++++ 2 files changed, 11 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 951af481da5a..da9ee466789b 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -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 diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c index 12561f96f0a2..278600143bb6 100644 --- a/kernel/rcu/rcuperf.c +++ b/kernel/rcu/rcuperf.c @@ -59,6 +59,7 @@ MODULE_AUTHOR("Paul E. McKenney "); 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; -- 2.39.5