From: Liang, Kan <kan.liang@linux.intel.com>
Date: Tue, 22 Oct 2019 09:13:09 +0000 (+0200)
Subject: perf/core: Optimize perf_init_event() for TYPE_SOFTWARE
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=d44f821b0e13275735e8f3fe4db8703b45f05d52;p=linux.git

perf/core: Optimize perf_init_event() for TYPE_SOFTWARE

Andi reported that he was hitting the linear search in
perf_init_event() a lot. Now that all !TYPE_SOFTWARE events should hit
the IDR, make sure the TYPE_SOFTWARE events are at the head of the
list such that we'll quickly find the right PMU (provided a valid
event was given).

Signed-off-by: Liang, Kan <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
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>
---

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4d67c5d35c137..cfd89b4a02d80 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10180,7 +10180,16 @@ got_cpu_context:
 	if (!pmu->event_idx)
 		pmu->event_idx = perf_event_idx_default;
 
-	list_add_rcu(&pmu->entry, &pmus);
+	/*
+	 * Ensure the TYPE_SOFTWARE PMUs are at the head of the list,
+	 * since these cannot be in the IDR. This way the linear search
+	 * is fast, provided a valid software event is provided.
+	 */
+	if (type == PERF_TYPE_SOFTWARE || !name)
+		list_add_rcu(&pmu->entry, &pmus);
+	else
+		list_add_tail_rcu(&pmu->entry, &pmus);
+
 	atomic_set(&pmu->exclusive_cnt, 0);
 	ret = 0;
 unlock: