[RFC][PATCH 08/12] perf: Optimize perf_sched_events usage

[Peter Zijlstra]

It doesn't make sense to take up-to _4_ references on
perf_sched_events per event, avoid doing this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 kernel/events/core.c |   22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3493,11 +3493,13 @@ static void unaccount_event_cpu(struct p
 
 static void unaccount_event(struct perf_event *event)
 {
+	bool dec = false;
+
 	if (event->parent)
 		return;
 
 	if (event->attach_state & PERF_ATTACH_TASK)
-		static_key_slow_dec_deferred(&perf_sched_events);
+		dec = true;
 	if (event->attr.mmap || event->attr.mmap_data)
 		atomic_dec(&nr_mmap_events);
 	if (event->attr.comm)
@@ -3507,12 +3509,15 @@ static void unaccount_event(struct perf_
 	if (event->attr.freq)
 		atomic_dec(&nr_freq_events);
 	if (event->attr.context_switch) {
-		static_key_slow_dec_deferred(&perf_sched_events);
+		dec = true;
 		atomic_dec(&nr_switch_events);
 	}
 	if (is_cgroup_event(event))
-		static_key_slow_dec_deferred(&perf_sched_events);
+		dec = true;
 	if (has_branch_stack(event))
+		dec = true;
+
+	if (dec)
 		static_key_slow_dec_deferred(&perf_sched_events);
 
 	unaccount_event_cpu(event, event->cpu);
@@ -7728,11 +7733,13 @@ static void account_event_cpu(struct per
 
 static void account_event(struct perf_event *event)
 {
+	bool inc = false;
+
 	if (event->parent)
 		return;
 
 	if (event->attach_state & PERF_ATTACH_TASK)
-		static_key_slow_inc(&perf_sched_events.key);
+		inc = true;
 	if (event->attr.mmap || event->attr.mmap_data)
 		atomic_inc(&nr_mmap_events);
 	if (event->attr.comm)
@@ -7745,11 +7752,14 @@ static void account_event(struct perf_ev
 	}
 	if (event->attr.context_switch) {
 		atomic_inc(&nr_switch_events);
-		static_key_slow_inc(&perf_sched_events.key);
+		inc = true;
 	}
 	if (has_branch_stack(event))
-		static_key_slow_inc(&perf_sched_events.key);
+		inc = true;
 	if (is_cgroup_event(event))
+		inc = true;
+
+	if (inc)
 		static_key_slow_inc(&perf_sched_events.key);
 
 	account_event_cpu(event, event->cpu);