From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752243AbdHJMHA (ORCPT ); Thu, 10 Aug 2017 08:07:00 -0400 Received: from terminus.zytor.com ([65.50.211.136]:42227 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751555AbdHJMG6 (ORCPT ); Thu, 10 Aug 2017 08:06:58 -0400 Date: Thu, 10 Aug 2017 05:03:19 -0700 From: "tip-bot for leilei.lin" Message-ID: Cc: hpa@zytor.com, mingo@kernel.org, leilei.lin@alibaba-inc.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, peterz@infradead.org Reply-To: peterz@infradead.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, leilei.lin@alibaba-inc.com, hpa@zytor.com, mingo@kernel.org In-Reply-To: <20170809002921.69813-1-leilei.lin@alibaba-inc.com> References: <20170809002921.69813-1-leilei.lin@alibaba-inc.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] perf/core: Reduce context switch overhead Git-Commit-ID: fdccc3fb7a42ea4e4cd77d2fb8fa3a45c66ec0bf X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: fdccc3fb7a42ea4e4cd77d2fb8fa3a45c66ec0bf Gitweb: http://git.kernel.org/tip/fdccc3fb7a42ea4e4cd77d2fb8fa3a45c66ec0bf Author: leilei.lin AuthorDate: Wed, 9 Aug 2017 08:29:21 +0800 Committer: Ingo Molnar CommitDate: Thu, 10 Aug 2017 12:08:40 +0200 perf/core: Reduce context switch overhead Skip most of the PMU context switching overhead when ctx->nr_events is 0. 50% performance overhead was observed under an extreme testcase. Signed-off-by: leilei.lin Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: acme@kernel.org Cc: alexander.shishkin@linux.intel.com Cc: eranian@gmail.com Cc: jolsa@redhat.com Cc: linxiulei@gmail.com Cc: yang_oliver@hotmail.com Link: http://lkml.kernel.org/r/20170809002921.69813-1-leilei.lin@alibaba-inc.com [ Rewrote the changelog. ] Signed-off-by: Ingo Molnar --- kernel/events/core.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index ee20d4c..d704e23 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3211,6 +3211,13 @@ static void perf_event_context_sched_in(struct perf_event_context *ctx, return; perf_ctx_lock(cpuctx, ctx); + /* + * We must check ctx->nr_events while holding ctx->lock, such + * that we serialize against perf_install_in_context(). + */ + if (!ctx->nr_events) + goto unlock; + perf_pmu_disable(ctx->pmu); /* * We want to keep the following priority order: @@ -3224,6 +3231,8 @@ static void perf_event_context_sched_in(struct perf_event_context *ctx, cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE); perf_event_sched_in(cpuctx, ctx, task); perf_pmu_enable(ctx->pmu); + +unlock: perf_ctx_unlock(cpuctx, ctx); }