From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752989Ab2G0DWd (ORCPT ); Thu, 26 Jul 2012 23:22:33 -0400 Received: from mailout-de.gmx.net ([213.165.64.22]:44314 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752681Ab2G0DWc (ORCPT ); Thu, 26 Jul 2012 23:22:32 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1/X8NtAmMPXoED6sSiCtmDiKZJCyeVMPVkEmWOeqN /iDP4n7NzoRZ59 Message-ID: <1343359346.6818.37.camel@marge.simpson.net> Subject: Re: [PATCH 1/2] sched: recover SD_WAKE_AFFINE in select_task_rq_fair and code clean up From: Mike Galbraith To: Alex Shi Cc: mingo@redhat.com, peterz@infradead.org, linux-kernel@vger.kernel.org, suresh.b.siddha@intel.com Date: Fri, 27 Jul 2012 05:22:26 +0200 In-Reply-To: <5011F323.10202@intel.com> References: <1343280446-24019-1-git-send-email-alex.shi@intel.com> <1343295457.6863.43.camel@marge.simpson.net> <5011F323.10202@intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2012-07-27 at 09:47 +0800, Alex Shi wrote: > On 07/26/2012 05:37 PM, Mike Galbraith wrote: > > > On Thu, 2012-07-26 at 13:27 +0800, Alex Shi wrote: > > > >> if (affine_sd) { > >> - if (cpu == prev_cpu || wake_affine(affine_sd, p, sync)) > >> + if (wake_affine(affine_sd, p, sync)) > >> prev_cpu = cpu; > >> > >> new_cpu = select_idle_sibling(p, prev_cpu); > > > > Hm, if cpu == prev_cpu, asking wake_affine() if it's ok to put wakee > > back where it came from is wasted cycles.. that's where the task is > > headed regardless of reply. > > > > -Mike > > > > > > > Sure. I modified the patch as below: (dang, plain text can't make upside down ack;) > === > From 610515185d8a98c14c7c339c25381bc96cd99d93 Mon Sep 17 00:00:00 2001 > From: Alex Shi > Date: Thu, 26 Jul 2012 08:55:34 +0800 > Subject: [PATCH 1/3] sched: recover SD_WAKE_AFFINE in select_task_rq_fair and > code clean up > > Since power saving code was removed from sched now, the implement > code is out of service in this function, and even pollute other logical. > like, 'want_sd' never has chance to be set '0', that remove the effect > of SD_WAKE_AFFINE here. > > So, clean up the obsolete code and some other unnecessary code. > > Signed-off-by: Alex Shi > --- > kernel/sched/fair.c | 32 +++----------------------------- > 1 files changed, 3 insertions(+), 29 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 22321db..53fd8db 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2686,7 +2686,6 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) > int prev_cpu = task_cpu(p); > int new_cpu = cpu; > int want_affine = 0; > - int want_sd = 1; > int sync = wake_flags & WF_SYNC; > > if (p->nr_cpus_allowed == 1) > @@ -2704,48 +2703,23 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) > continue; > > /* > - * If power savings logic is enabled for a domain, see if we > - * are not overloaded, if so, don't balance wider. > - */ > - if (tmp->flags & (SD_PREFER_LOCAL)) { > - unsigned long power = 0; > - unsigned long nr_running = 0; > - unsigned long capacity; > - int i; > - > - for_each_cpu(i, sched_domain_span(tmp)) { > - power += power_of(i); > - nr_running += cpu_rq(i)->cfs.nr_running; > - } > - > - capacity = DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE); > - > - if (nr_running < capacity) > - want_sd = 0; > - } > - > - /* > * If both cpu and prev_cpu are part of this domain, > * cpu is a valid SD_WAKE_AFFINE target. > */ > if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && > cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { > affine_sd = tmp; > - want_affine = 0; > - } > - > - if (!want_sd && !want_affine) > break; > + } > > if (!(tmp->flags & sd_flag)) > continue; > > - if (want_sd) > - sd = tmp; > + sd = tmp; > } > > if (affine_sd) { > - if (cpu == prev_cpu || wake_affine(affine_sd, p, sync)) > + if (cpu != prev_cpu && wake_affine(affine_sd, p, sync)) > prev_cpu = cpu; > > new_cpu = select_idle_sibling(p, prev_cpu);