[RFC][PATCH 1/9] perf: Optimize ctx_sched_out

[Peter Zijlstra]

Oleg noted that ctx_sched_out() disables the PMU even though it might
not actually do something, avoid needless PMU-disabling.

Reported-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 kernel/perf_event.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -1767,7 +1767,6 @@ static void ctx_sched_out(struct perf_ev
 	struct perf_event *event;
 
 	raw_spin_lock(&ctx->lock);
-	perf_pmu_disable(ctx->pmu);
 	ctx->is_active = 0;
 	if (likely(!ctx->nr_events))
 		goto out;
@@ -1777,6 +1776,7 @@ static void ctx_sched_out(struct perf_ev
 	if (!ctx->nr_active)
 		goto out;
 
+	perf_pmu_disable(ctx->pmu);
 	if (event_type & EVENT_PINNED) {
 		list_for_each_entry(event, &ctx->pinned_groups, group_entry)
 			group_sched_out(event, cpuctx, ctx);
@@ -1786,8 +1786,8 @@ static void ctx_sched_out(struct perf_ev
 		list_for_each_entry(event, &ctx->flexible_groups, group_entry)
 			group_sched_out(event, cpuctx, ctx);
 	}
-out:
 	perf_pmu_enable(ctx->pmu);
+out:
 	raw_spin_unlock(&ctx->lock);
 }
 


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