Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751875AbbDIHDa (ORCPT ); Thu, 9 Apr 2015 03:03:30 -0400 Received: from e23smtp01.au.ibm.com ([202.81.31.143]:59118 "EHLO e23smtp01.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751493AbbDIHD3 (ORCPT ); Thu, 9 Apr 2015 03:03:29 -0400 Date: Thu, 9 Apr 2015 12:32:20 +0530 From: Srikar Dronamraju To: Jason Low Cc: Preeti U Murthy , Morten Rasmussen , "peterz@infradead.org" , "mingo@kernel.org" , Daniel Lezcano , "riel@redhat.com" , "vincent.guittot@linaro.org" , "pjt@google.com" , "benh@kernel.crashing.org" , "efault@gmx.de" , "linux-kernel@vger.kernel.org" , "iamjoonsoo.kim@lge.com" , "svaidy@linux.vnet.ibm.com" , "tim.c.chen@linux.intel.com" Subject: Re: sched: Improve load balancing in the presence of idle CPUs Message-ID: <20150409070220.GA10331@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <551A5CCE.70008@linux.vnet.ibm.com> <1427828056.2492.24.camel@j-VirtualBox> <551B9514.80701@linux.vnet.ibm.com> <20150401170418.GX18994@e105550-lin.cambridge.arm.com> <1427954347.2556.43.camel@j-VirtualBox> <551FB5F5.5050906@linux.vnet.ibm.com> <1428449300.2556.79.camel@j-VirtualBox> <1428451666.2556.84.camel@j-VirtualBox> <20150408111216.GA24645@linux.vnet.ibm.com> <1428547155.3506.42.camel@j-VirtualBox> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1428547155.3506.42.camel@j-VirtualBox> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15040907-1618-0000-0000-000001E1FE92 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1644 Lines: 45 * Jason Low [2015-04-08 19:39:15]: > On Wed, 2015-04-08 at 16:42 +0530, Srikar Dronamraju wrote: > > * Jason Low [2015-04-07 17:07:46]: > > > @@ -7687,7 +7700,7 @@ static inline bool nohz_kick_needed(struct rq *rq) > > > int nr_busy, cpu = rq->cpu; > > > bool kick = false; > > > > > > - if (unlikely(rq->idle_balance)) > > > + if (unlikely(idle_cpu(cpu))) > > > return false; > > > > > > The only other place that we use idle_balance is > > run_rebalance_domains(). Would it make sense to just use idle_cpu() in > > run_rebalance_domains() and remove rq->idle_balance? > > Hi Srikar, > > So the idle_balance is used for storing the idle state of the CPU before > calling the softirq, for load balancing decisions. In that case, we may > need to keep this extra variable in order to store that information. > I am not sure if you got what I wanted to convey. rq->idle_balance gets updated at every scheduler_tick() but the only user of rq->idle_balance (after your change) seems to be run_rebalance_domains(). Now can we remove rq->idle_balance. This would mean we would have to call idle_cpu() instead of using rq->idle_balance in run_rebalance_domains(). (similar to what your above change) That way we can reduce the rq struct size and we might end up calling idle_cpu() lesser number of times. -- Thanks and Regards Srikar Dronamraju -- 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/