Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946108Ab3FUVXr (ORCPT ); Fri, 21 Jun 2013 17:23:47 -0400 Received: from mail-pb0-f42.google.com ([209.85.160.42]:47417 "EHLO mail-pb0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1946078Ab3FUVXp (ORCPT ); Fri, 21 Jun 2013 17:23:45 -0400 MIME-Version: 1.0 In-Reply-To: <51C47377.2000208@linux.intel.com> References: <20130530134718.GB32728@e103034-lin> <20130531105204.GE30394@gmail.com> <20130614160522.GG32728@e103034-lin> <51C07ABC.2080704@linux.intel.com> <51C1D0BB.3040705@linux.intel.com> <20130619170042.GH5460@e103034-lin> <51C1E58D.9000408@linux.intel.com> <20130621085002.GJ5460@e103034-lin> <51C47377.2000208@linux.intel.com> From: Catalin Marinas Date: Fri, 21 Jun 2013 22:23:25 +0100 X-Google-Sender-Auth: PoP5tbovHIjgTN95m8DnfXm-saU Message-ID: Subject: Re: power-efficient scheduling design To: Arjan van de Ven Cc: Morten Rasmussen , David Lang , "len.brown@intel.com" , "alex.shi@intel.com" , "corbet@lwn.net" , "peterz@infradead.org" , Linus Torvalds , "efault@gmx.de" , "linux-kernel@vger.kernel.org" , "linaro-kernel@lists.linaro.org" , "preeti@linux.vnet.ibm.com" , Andrew Morton , "pjt@google.com" , Ingo Molnar Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1284 Lines: 26 On 21 June 2013 16:38, Arjan van de Ven wrote: > On 6/21/2013 1:50 AM, Morten Rasmussen wrote: >> A hint when a task is moved to a new cpu is too late if the migration >> shouldn't have happened at all. If the scheduler knows that the cpu is >> able to switch to a higher p-state it can decide to wait for the p-state >> change instead of migrating the task and waking up another cpu. > > oops sorry I misread your mail (lack of early coffee I suppose) > > I can see your point of having a thing for "did we ask for all the performance > we could ask for" prior to doing a load balance (although, for power efficiency, > if you have two tasks that could run in parallel, it's usually better to > run them in parallel... so likely we should balance anyway) Not necessarily, especially if parallel running implies powering up a full cluster just for one CPU (it depends on the hardware but for example a cluster may not be able to go in deeper sleep states unless all the CPUs in that cluster are idle). -- Catalin -- 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/