perf_events: Add perf_event_time()

Adds perf_event_time() to try and centralize access to event
timing and in particular ctx->time. Prepares for cgroup support.
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4d22059c.122ae30a.5e0e.ffff8b8b@mx.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/perf_event.c

@@ -268,6 +268,12 @@ static void update_context_time(struct perf_event_context *ctx)
 	ctx->timestamp = now;
 }
 
+static u64 perf_event_time(struct perf_event *event)
+{
+	struct perf_event_context *ctx = event->ctx;
+	return ctx ? ctx->time : 0;
+}
+
 /*
  * Update the total_time_enabled and total_time_running fields for a event.
  */
@@ -281,7 +287,7 @@ static void update_event_times(struct perf_event *event)
 		return;
 
 	if (ctx->is_active)
-		run_end = ctx->time;
+		run_end = perf_event_time(event);
 	else
 		run_end = event->tstamp_stopped;
 
@@ -290,7 +296,7 @@ static void update_event_times(struct perf_event *event)
 	if (event->state == PERF_EVENT_STATE_INACTIVE)
 		run_end = event->tstamp_stopped;
 	else
-		run_end = ctx->time;
+		run_end = perf_event_time(event);
 
 	event->total_time_running = run_end - event->tstamp_running;
 }
@@ -546,6 +552,7 @@ event_sched_out(struct perf_event *event,
 		  struct perf_cpu_context *cpuctx,
 		  struct perf_event_context *ctx)
 {
+	u64 tstamp = perf_event_time(event);
 	u64 delta;
 	/*
 	 * An event which could not be activated because of
@@ -557,7 +564,7 @@ event_sched_out(struct perf_event *event,
 	    && !event_filter_match(event)) {
 		delta = ctx->time - event->tstamp_stopped;
 		event->tstamp_running += delta;
-		event->tstamp_stopped = ctx->time;
+		event->tstamp_stopped = tstamp;
 	}
 
 	if (event->state != PERF_EVENT_STATE_ACTIVE)
@@ -568,7 +575,7 @@ event_sched_out(struct perf_event *event,
 		event->pending_disable = 0;
 		event->state = PERF_EVENT_STATE_OFF;
 	}
-	event->tstamp_stopped = ctx->time;
+	event->tstamp_stopped = tstamp;
 	event->pmu->del(event, 0);
 	event->oncpu = -1;
 
@@ -780,6 +787,8 @@ event_sched_in(struct perf_event *event,
 		 struct perf_cpu_context *cpuctx,
 		 struct perf_event_context *ctx)
 {
+	u64 tstamp = perf_event_time(event);
+
 	if (event->state <= PERF_EVENT_STATE_OFF)
 		return 0;
 
@@ -796,9 +805,9 @@ event_sched_in(struct perf_event *event,
 		return -EAGAIN;
 	}
 
-	event->tstamp_running += ctx->time - event->tstamp_stopped;
+	event->tstamp_running += tstamp - event->tstamp_stopped;
 
-	event->shadow_ctx_time = ctx->time - ctx->timestamp;
+	event->shadow_ctx_time = tstamp - ctx->timestamp;
 
 	if (!is_software_event(event))
 		cpuctx->active_oncpu++;
@@ -910,11 +919,13 @@ static int group_can_go_on(struct perf_event *event,
 static void add_event_to_ctx(struct perf_event *event,
 			       struct perf_event_context *ctx)
 {
+	u64 tstamp = perf_event_time(event);
+
 	list_add_event(event, ctx);
 	perf_group_attach(event);
-	event->tstamp_enabled = ctx->time;
-	event->tstamp_running = ctx->time;
-	event->tstamp_stopped = ctx->time;
+	event->tstamp_enabled = tstamp;
+	event->tstamp_running = tstamp;
+	event->tstamp_stopped = tstamp;
 }
 
 /*
@@ -1054,14 +1065,13 @@ static void __perf_event_mark_enabled(struct perf_event *event,
 					struct perf_event_context *ctx)
 {
 	struct perf_event *sub;
+	u64 tstamp = perf_event_time(event);
 
 	event->state = PERF_EVENT_STATE_INACTIVE;
-	event->tstamp_enabled = ctx->time - event->total_time_enabled;
+	event->tstamp_enabled = tstamp - event->total_time_enabled;
 	list_for_each_entry(sub, &event->sibling_list, group_entry) {
-		if (sub->state >= PERF_EVENT_STATE_INACTIVE) {
-			sub->tstamp_enabled =
-				ctx->time - sub->total_time_enabled;
-		}
+		if (sub->state >= PERF_EVENT_STATE_INACTIVE)
+			sub->tstamp_enabled = tstamp - sub->total_time_enabled;
 	}
 }