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Commit 8703a7cf authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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perf/core: Fix tree based event rotation 



Similar to how first programming cpu=-1 and then cpu=# is wrong, so is
rotating both. It was especially wrong when we were still programming
the PMU in this same order, because in that scenario we might never
actually end up running cpu=# events at all.

Cure this by using the active_list to pick the rotation event; since
at programming we already select the left-most event.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Carrillo-Cisneros <davidcc@google.com>
Cc: Dmitri Prokhorov <Dmitry.Prohorov@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Valery Cherepennikov <valery.cherepennikov@intel.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 6e6804d2

kernel/events/core.c

+18 −26
Original line number Diff line number Diff line
@@ -1623,22 +1623,6 @@ perf_event_groups_next(struct perf_event *event) 
	return NULL;

}



/*

 * Rotate the @cpu subtree.

 *

 * Re-insert the leftmost event at the tail of the subtree.

 */

static void

perf_event_groups_rotate(struct perf_event_groups *groups, int cpu)

{

	struct perf_event *event = perf_event_groups_first(groups, cpu);



	if (event) {

		perf_event_groups_delete(groups, event);

		perf_event_groups_insert(groups, event);

	}

}



/*

 * Iterate through the whole groups tree.

 */
@@ -3601,24 +3585,24 @@ static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx, 
}



/*

 * Round-robin a context's events:

 * Move @event to the tail of the @ctx's elegible events.

 */

static void rotate_ctx(struct perf_event_context *ctx)

static void rotate_ctx(struct perf_event_context *ctx, struct perf_event *event)

{

	/*

	 * Rotate the first entry last of non-pinned groups. Rotation might be

	 * disabled by the inheritance code.

	 */

	if (!ctx->rotate_disable) {

		int sw = -1, cpu = smp_processor_id();

	if (ctx->rotate_disable)

		return;



		perf_event_groups_rotate(&ctx->flexible_groups, sw);

		perf_event_groups_rotate(&ctx->flexible_groups, cpu);

	}

	perf_event_groups_delete(&ctx->flexible_groups, event);

	perf_event_groups_insert(&ctx->flexible_groups, event);

}



static int perf_rotate_context(struct perf_cpu_context *cpuctx)

{

	struct perf_event *ctx_event = NULL, *cpuctx_event = NULL;

	struct perf_event_context *ctx = NULL;

	int rotate = 0;
@@ -3639,13 +3623,21 @@ static int perf_rotate_context(struct perf_cpu_context *cpuctx) 
	perf_ctx_lock(cpuctx, cpuctx->task_ctx);

	perf_pmu_disable(cpuctx->ctx.pmu);



	cpuctx_event = list_first_entry_or_null(&cpuctx->ctx.flexible_active,

						struct perf_event, active_list);

	if (ctx) {

		ctx_event = list_first_entry_or_null(&ctx->flexible_active,

						     struct perf_event, active_list);

	}



	cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);

	if (ctx)

		ctx_sched_out(ctx, cpuctx, EVENT_FLEXIBLE);



	rotate_ctx(&cpuctx->ctx);

	if (ctx)

		rotate_ctx(ctx);

	if (cpuctx_event)

		rotate_ctx(&cpuctx->ctx, cpuctx_event);

	if (ctx_event)

		rotate_ctx(ctx, ctx_event);



	perf_event_sched_in(cpuctx, ctx, current);