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From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
	mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
	"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 05/30] refperf: Add holdoff parameter to allow CPUs to come online
Date: Mon, 22 Jun 2020 17:29:48 -0700
Message-ID: <20200623003013.26252-5-paulmck@kernel.org> (raw)
In-Reply-To: <20200623002941.GA26089@paulmck-ThinkPad-P72>

From: "Paul E. McKenney" <paulmck@kernel.org>

This commit adds an rcuperf module parameter named "holdoff" that
defaults to 10 seconds if refperf is built in and to zero otherwise.
The assumption is that all the CPUs are online by the time that the
modprobe and insmod commands are going to do anything, and that normal
systems will have all the CPUs online within ten seconds.

Larger systems may take many tens of seconds or even minutes to get
to this point, hence this being a module parameter instead of being a
hard-coded constant.

Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/refperf.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/refperf.c b/kernel/rcu/refperf.c
index 6116153..4d686fd 100644
--- a/kernel/rcu/refperf.c
+++ b/kernel/rcu/refperf.c
@@ -57,7 +57,10 @@ MODULE_PARM_DESC(perf_type, "Type of test (rcu, srcu, refcnt, rwsem, rwlock.");
 
 torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
 
-// Number of loops per experiment, all readers execute an operation concurrently
+// Wait until there are multiple CPUs before starting test.
+torture_param(int, holdoff, IS_BUILTIN(CONFIG_RCU_REF_PERF_TEST) ? 10 : 0,
+	      "Holdoff time before test start (s)");
+// Number of loops per experiment, all readers execute operations concurrently.
 torture_param(long, loops, 10000000, "Number of loops per experiment.");
 
 #ifdef MODULE
@@ -248,6 +251,8 @@ ref_perf_reader(void *arg)
 	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
 	set_user_nice(current, MAX_NICE);
 	atomic_inc(&n_init);
+	if (holdoff)
+		schedule_timeout_interruptible(holdoff * HZ);
 repeat:
 	VERBOSE_PERFOUT("ref_perf_reader %ld: waiting to start next experiment on cpu %d", me, smp_processor_id());
 
@@ -357,6 +362,8 @@ static int main_func(void *arg)
 
 	// Wait for all threads to start.
 	wait_event(main_wq, atomic_read(&n_init) == (nreaders + 1));
+	if (holdoff)
+		schedule_timeout_interruptible(holdoff * HZ);
 
 	// Start exp readers up per experiment
 	for (exp = 0; exp < nreaders && !torture_must_stop(); exp++) {
@@ -420,8 +427,8 @@ static void
 ref_perf_print_module_parms(struct ref_perf_ops *cur_ops, const char *tag)
 {
 	pr_alert("%s" PERF_FLAG
-		 "--- %s:  verbose=%d shutdown=%d loops=%ld\n", perf_type, tag,
-		 verbose, shutdown, loops);
+		 "--- %s:  verbose=%d shutdown=%d holdoff=%d loops=%ld\n", perf_type, tag,
+		 verbose, shutdown, holdoff, loops);
 }
 
 static void
-- 
2.9.5


  parent reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23  0:29 [PATCH tip/core/rcu 0/30] Add read-side scalability tests for v5.9 Paul E. McKenney
2020-06-23  0:29 ` [PATCH tip/core/rcu 01/30] rcuperf: Remove useless while loops around wait_event paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 02/30] refperf: Add a test to measure performance of read-side synchronization paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 03/30] rcuperf: Add comments explaining the high reader overhead paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 04/30] torture: Add refperf to the rcutorture scripting paulmck
2020-06-23  0:29 ` paulmck [this message]
2020-06-23  0:29 ` [PATCH tip/core/rcu 06/30] refperf: Hoist function-pointer calls out of the loop paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 07/30] refperf: Allow decimal nanoseconds paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 08/30] refperf: Convert nreaders to a module parameter paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 09/30] refperf: Provide module parameter to specify number of experiments paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 10/30] refperf: Dynamically allocate experiment-summary output buffer paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 11/30] refperf: Dynamically allocate thread-summary " paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 12/30] refperf: Make functions static paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 13/30] refperf: Tune reader measurement interval paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 14/30] refperf: Convert reader_task structure's "start" field to int paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 15/30] refperf: More closely synchronize reader start times paulmck
2020-06-23  0:29 ` [PATCH tip/core/rcu 16/30] refperf: Add warmup and cooldown processing phases paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 17/30] refperf: Label experiment-number column "Runs" paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 18/30] refperf: Output per-experiment data points paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 19/30] refperf: Simplify initialization-time wakeup protocol paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 20/30] refperf: Add read-side delay module parameter paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 21/30] refperf: Adjust refperf.loop default value paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 22/30] doc: Document rcuperf's module parameters paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 23/30] refperf: Work around 64-bit division paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 24/30] refperf: Change readdelay module parameter to nanoseconds paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 25/30] refperf: Add test for RCU Tasks Trace readers paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 26/30] refperf: Add test for RCU Tasks readers paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 27/30] rcu-tasks: Fix synchronize_rcu_tasks_trace() header comment paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 28/30] refperf: Rename RCU_REF_PERF_TEST to RCU_REF_SCALE_TEST paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 29/30] refperf: Rename refperf.c to refscale.c and change internal names paulmck
2020-06-23  0:30 ` [PATCH tip/core/rcu 30/30] refscale: Change --torture type from refperf to refscale paulmck

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