perf: Optimize context ops

Assuming we don't mix events of different pmus onto a single context
(with the exeption of software events inside a hardware group) we can
now assume that all events on a particular context belong to the same
pmu, hence we can disable the pmu for the entire context operations.

This reduces the amount of hardware writes.

The exception for swevents comes from the fact that the sw pmu disable
is a nop.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: paulus <paulus@samba.org>
Cc: stephane eranian <eranian@googlemail.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Lin Ming <ming.m.lin@intel.com>
Cc: Yanmin <yanmin_zhang@linux.intel.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/perf_event.c

@@ -1065,6 +1065,7 @@ static void ctx_sched_out(struct perf_event_context *ctx,
 	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;
@@ -1083,6 +1084,7 @@ static void ctx_sched_out(struct perf_event_context *ctx,
 			group_sched_out(event, cpuctx, ctx);
 	}
 out:
+	perf_pmu_enable(ctx->pmu);
 	raw_spin_unlock(&ctx->lock);
 }
 
@@ -1400,6 +1402,7 @@ void perf_event_context_sched_in(struct perf_event_context *ctx)
 	if (cpuctx->task_ctx == ctx)
 		return;
 
+	perf_pmu_disable(ctx->pmu);
 	/*
 	 * We want to keep the following priority order:
 	 * cpu pinned (that don't need to move), task pinned,
@@ -1418,6 +1421,7 @@ void perf_event_context_sched_in(struct perf_event_context *ctx)
 	 * cpu-context we got scheduled on is actually rotating.
 	 */
 	perf_pmu_rotate_start(ctx->pmu);
+	perf_pmu_enable(ctx->pmu);
 }
 
 /*
@@ -1629,6 +1633,7 @@ static enum hrtimer_restart perf_event_context_tick(struct hrtimer *timer)
 			rotate = 1;
 	}
 
+	perf_pmu_disable(cpuctx->ctx.pmu);
 	perf_ctx_adjust_freq(&cpuctx->ctx, cpuctx->timer_interval);
 	if (ctx)
 		perf_ctx_adjust_freq(ctx, cpuctx->timer_interval);
@@ -1649,6 +1654,7 @@ static enum hrtimer_restart perf_event_context_tick(struct hrtimer *timer)
 		task_ctx_sched_in(ctx, EVENT_FLEXIBLE);
 
 done:
+	perf_pmu_enable(cpuctx->ctx.pmu);
 	hrtimer_forward_now(timer, ns_to_ktime(cpuctx->timer_interval));
 
 	return restart;