Commit e76506f0 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

refscale: Allow summarization of verbose output 



The refscale test prints enough per-kthread console output to provoke RCU
CPU stall warnings on large systems.  This commit therefore allows this
output to be summarized.  For example, the refscale.verbose_batched=32
boot parameter would causes only every 32nd line of output to be logged.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent f3ea978b

Documentation/admin-guide/kernel-parameters.txt

+6 −0
Original line number Diff line number Diff line
@@ -4557,6 +4557,12 @@ 
	refscale.verbose= [KNL]

			Enable additional printk() statements.



	refscale.verbose_batched= [KNL]

			Batch the additional printk() statements.  If zero

			(the default) or negative, print everything.  Otherwise,

			print every Nth verbose statement, where N is the value

			specified.



	relax_domain_level=

			[KNL, SMP] Set scheduler's default relax_domain_level.

			See Documentation/admin-guide/cgroup-v1/cpusets.rst.

kernel/rcu/refscale.c

+16 −5
Original line number Diff line number Diff line
@@ -46,6 +46,16 @@ 
#define VERBOSE_SCALEOUT(s, x...) \

	do { if (verbose) pr_alert("%s" SCALE_FLAG s, scale_type, ## x); } while (0)



static atomic_t verbose_batch_ctr;



#define VERBOSE_SCALEOUT_BATCH(s, x...)							\

do {											\

	if (verbose &&									\

	    (verbose_batched <= 0 ||							\

	     !(atomic_inc_return(&verbose_batch_ctr) % verbose_batched)))		\

		pr_alert("%s" SCALE_FLAG s, scale_type, ## x);				\

} while (0)



#define VERBOSE_SCALEOUT_ERRSTRING(s, x...) \

	do { if (verbose) pr_alert("%s" SCALE_FLAG "!!! " s, scale_type, ## x); } while (0)
@@ -57,6 +67,7 @@ module_param(scale_type, charp, 0444); 
MODULE_PARM_DESC(scale_type, "Type of test (rcu, srcu, refcnt, rwsem, rwlock.");



torture_param(int, verbose, 0, "Enable verbose debugging printk()s");

torture_param(int, verbose_batched, 0, "Batch verbose debugging printk()s");



// Wait until there are multiple CPUs before starting test.

torture_param(int, holdoff, IS_BUILTIN(CONFIG_RCU_REF_SCALE_TEST) ? 10 : 0,
@@ -368,14 +379,14 @@ ref_scale_reader(void *arg) 
	u64 start;

	s64 duration;



	VERBOSE_SCALEOUT("ref_scale_reader %ld: task started", me);

	VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: task started", me);

	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_SCALEOUT("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, smp_processor_id());

	VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, smp_processor_id());



	// Wait for signal that this reader can start.

	wait_event(rt->wq, (atomic_read(&nreaders_exp) && smp_load_acquire(&rt->start_reader)) ||
@@ -392,7 +403,7 @@ ref_scale_reader(void *arg) 
		while (atomic_read_acquire(&n_started))

			cpu_relax();



	VERBOSE_SCALEOUT("ref_scale_reader %ld: experiment %d started", me, exp_idx);

	VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: experiment %d started", me, exp_idx);





	// To reduce noise, do an initial cache-warming invocation, check
@@ -421,7 +432,7 @@ ref_scale_reader(void *arg) 
	if (atomic_dec_and_test(&nreaders_exp))

		wake_up(&main_wq);



	VERBOSE_SCALEOUT("ref_scale_reader %ld: experiment %d ended, (readers remaining=%d)",

	VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: experiment %d ended, (readers remaining=%d)",

				me, exp_idx, atomic_read(&nreaders_exp));



	if (!torture_must_stop())