From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754846AbZIRTzF (ORCPT ); Fri, 18 Sep 2009 15:55:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753975AbZIRTzA (ORCPT ); Fri, 18 Sep 2009 15:55:00 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:48805 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753919AbZIRTy7 (ORCPT ); Fri, 18 Sep 2009 15:54:59 -0400 Date: Fri, 18 Sep 2009 21:54:55 +0200 From: Ingo Molnar To: Mark Langsdorf , Peter Zijlstra , Mike Galbraith Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] Prevent immediate process rescheduling Message-ID: <20090918195455.GC11726@elte.hu> References: <200909181449.12311.mark.langsdorf@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200909181449.12311.mark.langsdorf@amd.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (fixed the Cc: lines) * Mark Langsdorf wrote: > Prevent the scheduler from immediately rescheduling a process > that just yielded if there is another process available. > > Originally suggested by Mike Galbraith (efault@gmx.de). > > Signed-off-by: Mark Langsdorf > --- > kernel/sched_fair.c | 16 +++++++++++++++- > 1 files changed, 15 insertions(+), 1 deletions(-) > > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > index 652e8bd..4fad08f 100644 > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -353,11 +353,25 @@ static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) > static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq) > { > struct rb_node *left = cfs_rq->rb_leftmost; > + struct sched_entity *se, *curr; > > if (!left) > return NULL; > > - return rb_entry(left, struct sched_entity, run_node); > + se = rb_entry(left, struct sched_entity, run_node); > + curr = ¤t->se; > + > + /* > + * Don't select the entity who just tried to schedule away > + * if there's another entity available. > + */ > + if (unlikely(se == curr && cfs_rq->nr_running > 1)) { > + struct rb_node *next_node = rb_next(&curr->run_node); > + if (next_node) > + se = rb_entry(next_node, struct sched_entity, run_node); > + } > + > + return se; > } I suspect some real workload is the motivation of this - what is that workload? Ingo