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Commit d4944a06 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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perf: Provide better condition for event rotation 



Try to avoid useless rotation and PMU disables.

[ Could be improved by keeping a nr_runnable count to better account
  for the < PERF_STAT_INACTIVE counters ]

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: paulus@samba.org
Cc: eranian@google.com
Cc: robert.richter@amd.com
Cc: fweisbec@gmail.com
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f3d46b2e

kernel/perf_event.c

+15 −6
Original line number Diff line number Diff line
@@ -1524,12 +1524,15 @@ static void perf_ctx_adjust_freq(struct perf_event_context *ctx) 
		 */

		if (interrupts == MAX_INTERRUPTS) {

			perf_log_throttle(event, 1);

			perf_disable();

			event->pmu->unthrottle(event);

			perf_enable();

		}



		if (!event->attr.freq || !event->attr.sample_freq)

			continue;



		perf_disable();

		event->pmu->read(event);

		now = atomic64_read(&event->count);

		delta = now - hwc->freq_count_stamp;
@@ -1537,6 +1540,7 @@ static void perf_ctx_adjust_freq(struct perf_event_context *ctx) 


		if (delta > 0)

			perf_adjust_period(event, TICK_NSEC, delta);

		perf_enable();

	}

	raw_spin_unlock(&ctx->lock);

}
@@ -1546,9 +1550,6 @@ static void perf_ctx_adjust_freq(struct perf_event_context *ctx) 
 */

static void rotate_ctx(struct perf_event_context *ctx)

{

	if (!ctx->nr_events)

		return;



	raw_spin_lock(&ctx->lock);



	/* Rotate the first entry last of non-pinned groups */
@@ -1561,19 +1562,28 @@ void perf_event_task_tick(struct task_struct *curr) 
{

	struct perf_cpu_context *cpuctx;

	struct perf_event_context *ctx;

	int rotate = 0;



	if (!atomic_read(&nr_events))

		return;



	cpuctx = &__get_cpu_var(perf_cpu_context);

	ctx = curr->perf_event_ctxp;

	if (cpuctx->ctx.nr_events &&

	    cpuctx->ctx.nr_events != cpuctx->ctx.nr_active)

		rotate = 1;



	perf_disable();

	ctx = curr->perf_event_ctxp;

	if (ctx && ctx->nr_events && ctx->nr_events != ctx->nr_active)

		rotate = 1;



	perf_ctx_adjust_freq(&cpuctx->ctx);

	if (ctx)

		perf_ctx_adjust_freq(ctx);



	if (!rotate)

		return;



	perf_disable();

	cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);

	if (ctx)

		task_ctx_sched_out(ctx, EVENT_FLEXIBLE);
@@ -1585,7 +1595,6 @@ void perf_event_task_tick(struct task_struct *curr) 
	cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE);

	if (ctx)

		task_ctx_sched_in(curr, EVENT_FLEXIBLE);



	perf_enable();

}