From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753895Ab1C1PBP (ORCPT ); Mon, 28 Mar 2011 11:01:15 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:41026 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751205Ab1C1PBO convert rfc822-to-8bit (ORCPT ); Mon, 28 Mar 2011 11:01:14 -0400 Subject: Re: [PATCH,RFC] perf: panic due to inclied cpu context task_ctx value From: Peter Zijlstra To: Oleg Nesterov Cc: Jiri Olsa , Paul Mackerras , Ingo Molnar , linux-kernel@vger.kernel.org In-Reply-To: <1301324275.4859.25.camel@twins> References: <20110324164436.GC1930@jolsa.brq.redhat.com> <1301153868.2250.359.camel@laptop> <20110326161346.GA18272@redhat.com> <1301157483.2250.366.camel@laptop> <20110326170922.GA20329@redhat.com> <20110326173545.GA22919@redhat.com> <1301164168.2250.370.camel@laptop> <20110328133033.GA8254@redhat.com> <1301324275.4859.25.camel@twins> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Mon, 28 Mar 2011 17:00:49 +0200 Message-ID: <1301324449.4859.26.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2011-03-28 at 16:57 +0200, Peter Zijlstra wrote: > > --- > Subject: perf: Optimize ctx_sched_out > From: Peter Zijlstra > Date: Mon Mar 28 16:55:36 CEST 2011 > > Oleg noted that ctx_sched_out() disables the PMU even though it might > not actually do something, avoid needless PMU-disabling. > > Reported-by: Oleg Nesterov > Signed-off-by: Peter Zijlstra > LKML-Reference: > --- > kernel/perf_event.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > Index: linux-2.6/kernel/perf_event.c > =================================================================== > --- linux-2.6.orig/kernel/perf_event.c > +++ linux-2.6/kernel/perf_event.c > @@ -1767,7 +1767,6 @@ static void ctx_sched_out(struct perf_ev > struct perf_event *event; > > raw_spin_lock(&ctx->lock); > - perf_pmu_disable(ctx->pmu); > ctx->is_active = 0; > if (likely(!ctx->nr_events)) > goto out; > @@ -1777,6 +1776,7 @@ static void ctx_sched_out(struct perf_ev > if (!ctx->nr_active) > goto out; > > + perf_pmu_disable(ctx->pmu); > if (event_type & EVENT_PINNED) { > list_for_each_entry(event, &ctx->pinned_groups, group_entry) > group_sched_out(event, cpuctx, ctx); > @@ -1786,8 +1786,8 @@ static void ctx_sched_out(struct perf_ev > list_for_each_entry(event, &ctx->flexible_groups, group_entry) > group_sched_out(event, cpuctx, ctx); > } > -out: > perf_pmu_enable(ctx->pmu); > +out: > raw_spin_unlock(&ctx->lock); > } We could probably remove the PMU disabling all together, but that would involve like actual thinking :-)