linux-kernel - [tip: perf/core] perf/core: Optimize perf_init_event() for TYPE

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Date:   Mon, 28 Oct 2019 12:43:17 -0000
From:   "tip-bot2 for Liang, Kan" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Liang, Kan" <kan.liang@...ux.intel.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vince Weaver <vincent.weaver@...ne.edu>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf/core: Optimize perf_init_event() for TYPE_SOFTWARE

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     d44f821b0e13275735e8f3fe4db8703b45f05d52
Gitweb:        https://git.kernel.org/tip/d44f821b0e13275735e8f3fe4db8703b45f05d52
Author:        Liang, Kan <kan.liang@...ux.intel.com>
AuthorDate:    Tue, 22 Oct 2019 11:13:09 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Mon, 28 Oct 2019 12:53:28 +01:00

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@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Vince Weaver <vincent.weaver@...ne.edu>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/events/core.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4d67c5d..cfd89b4 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: