From 25432ae96a9889774a05bf5f0f6fd8dbcdec5e72 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri, 8 Jan 2016 11:05:09 +0100
Subject: [PATCH] perf: Optimize perf_sched_events() usage

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@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/events/core.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 079eb9fcaaa8..935aefd16354 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3491,11 +3491,13 @@ static void unaccount_event_cpu(struct perf_event *event, int cpu)
 
 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)
@@ -3505,12 +3507,15 @@ static void unaccount_event(struct perf_event *event)
 	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);
@@ -7723,11 +7728,13 @@ static void account_event_cpu(struct perf_event *event, int cpu)
 
 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)
@@ -7740,11 +7747,14 @@ static void account_event(struct perf_event *event)
 	}
 	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);