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Commit d9494cb4 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf: Remove useless atomic_t 



There's nothing atomic about atomic_set vs atomic_read; so remove the
atomic_t usage.

Also, make running_sample_length static as it really is (and should
be) local to this translation unit.

Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: eranian@google.com
Cc: Don Zickus <dzickus@redhat.com>
Cc: jmario@redhat.com
Cc: acme@infradead.org
Cc: dave.hansen@linux.intel.com
Link: http://lkml.kernel.org/n/tip-vw9lg588x1ic248whybjon0c@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent aac89854

kernel/events/core.c

+9 −9
Original line number Diff line number Diff line
@@ -175,8 +175,8 @@ int sysctl_perf_event_sample_rate __read_mostly = DEFAULT_MAX_SAMPLE_RATE; 
static int max_samples_per_tick __read_mostly	= DIV_ROUND_UP(DEFAULT_MAX_SAMPLE_RATE, HZ);

static int perf_sample_period_ns __read_mostly	= DEFAULT_SAMPLE_PERIOD_NS;



static atomic_t perf_sample_allowed_ns __read_mostly =

	ATOMIC_INIT( DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100);

static int perf_sample_allowed_ns __read_mostly =

	DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100;



void update_perf_cpu_limits(void)

{
@@ -184,7 +184,7 @@ void update_perf_cpu_limits(void) 


	tmp *= sysctl_perf_cpu_time_max_percent;

	do_div(tmp, 100);

	atomic_set(&perf_sample_allowed_ns, tmp);

	ACCESS_ONCE(perf_sample_allowed_ns) = tmp;

}



static int perf_rotate_context(struct perf_cpu_context *cpuctx);
@@ -228,14 +228,15 @@ int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write, 
 * we detect that events are taking too long.

 */

#define NR_ACCUMULATED_SAMPLES 128

DEFINE_PER_CPU(u64, running_sample_length);

static DEFINE_PER_CPU(u64, running_sample_length);



void perf_sample_event_took(u64 sample_len_ns)

{

	u64 avg_local_sample_len;

	u64 local_samples_len;

	u64 allowed_ns = ACCESS_ONCE(perf_sample_allowed_ns);



	if (atomic_read(&perf_sample_allowed_ns) == 0)

	if (allowed_ns == 0)

		return;



	/* decay the counter by 1 average sample */
@@ -251,7 +252,7 @@ void perf_sample_event_took(u64 sample_len_ns) 
	 */

	avg_local_sample_len = local_samples_len/NR_ACCUMULATED_SAMPLES;



	if (avg_local_sample_len <= atomic_read(&perf_sample_allowed_ns))

	if (avg_local_sample_len <= allowed_ns)

		return;



	if (max_samples_per_tick <= 1)
@@ -262,10 +263,9 @@ void perf_sample_event_took(u64 sample_len_ns) 
	perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;



	printk_ratelimited(KERN_WARNING

			"perf samples too long (%lld > %d), lowering "

			"perf samples too long (%lld > %lld), lowering "

			"kernel.perf_event_max_sample_rate to %d\n",

			avg_local_sample_len,

			atomic_read(&perf_sample_allowed_ns),

			avg_local_sample_len, allowed_ns,

			sysctl_perf_event_sample_rate);



	update_perf_cpu_limits();