Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756370AbaDXLcm (ORCPT ); Thu, 24 Apr 2014 07:32:42 -0400 Received: from casper.infradead.org ([85.118.1.10]:36711 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756024AbaDXLch (ORCPT ); Thu, 24 Apr 2014 07:32:37 -0400 Date: Thu, 24 Apr 2014 13:32:31 +0200 From: Peter Zijlstra To: Morten Rasmussen Cc: Jason Low , "mingo@kernel.org" , "linux-kernel@vger.kernel.org" , "daniel.lezcano@linaro.org" , "alex.shi@linaro.org" , "preeti@linux.vnet.ibm.com" , "efault@gmx.de" , "vincent.guittot@linaro.org" , "aswin@hp.com" , "chegu_vinod@hp.com" Subject: Re: [PATCH 3/3] sched, fair: Stop searching for tasks in newidle balance if there are runnable tasks Message-ID: <20140424113231.GR11096@twins.programming.kicks-ass.net> References: <1398303035-18255-1-git-send-email-jason.low2@hp.com> <1398303035-18255-4-git-send-email-jason.low2@hp.com> <20140424103059.GL2500@e103034-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140424103059.GL2500@e103034-lin> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 24, 2014 at 11:30:59AM +0100, Morten Rasmussen wrote: > On Thu, Apr 24, 2014 at 02:30:35AM +0100, Jason Low wrote: > > @@ -6704,7 +6703,12 @@ static int idle_balance(struct rq *this_rq) > > interval = msecs_to_jiffies(sd->balance_interval); > > if (time_after(next_balance, sd->last_balance + interval)) > > next_balance = sd->last_balance + interval; > > - if (pulled_task) > > + > > + /* > > + * Stop searching for tasks to pull if there are > > + * now runnable tasks on this rq. > > + */ > > + if (pulled_task || this_rq->nr_running > 0) > > Should this be cfs tasks instead? > > + if (pulled_task || this_rq->cfs.h_nr_running > 0) > > 3.15-rc2 commit 35805ff8f4fc535ac85330170d3c56829c87c677 seems to > indicate that using rq->nr_running may lead to trouble. > > The other two patches look good to me. No, this really wants to be nr_running, we want to bail the idle balancer when there's anything runnable present. Note how out: is very careful to return -1 (which results in RETRY_TASK) when rq->nr_running != rq->cfs.h_nr_running. That same out: test also makes problem that commit fixes impossible again. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/