Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946127Ab3FUVeD (ORCPT ); Fri, 21 Jun 2013 17:34:03 -0400 Received: from mga09.intel.com ([134.134.136.24]:27622 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1945979Ab3FUVeB (ORCPT ); Fri, 21 Jun 2013 17:34:01 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,915,1363158000"; d="scan'208";a="333565432" Message-ID: <51C4C6C8.1050008@linux.intel.com> Date: Fri, 21 Jun 2013 14:34:00 -0700 From: Arjan van de Ven User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130509 Thunderbird/17.0.6 MIME-Version: 1.0 To: Catalin Marinas 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 Subject: Re: power-efficient scheduling design 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> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1348 Lines: 34 On 6/21/2013 2:23 PM, Catalin Marinas wrote: >> >> 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). I guess it depends on the system the very first cpu needs to power on * the core itself * the "cluster" that you mention * the memory controller * the memory (out of self refresh) while the second cpu needs * the core itself * maybe a second cluster normally on Intel systems, the memory power delta is quite significant which then means the efficiency of the second core is huge compared to running things in sequence. -- 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/