Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932592Ab2HVNXS (ORCPT ); Wed, 22 Aug 2012 09:23:18 -0400 Received: from mga01.intel.com ([192.55.52.88]:34252 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751972Ab2HVNXP (ORCPT ); Wed, 22 Aug 2012 09:23:15 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.77,808,1336374000"; d="scan'208";a="208485835" Message-ID: <5034DD35.9090504@linux.intel.com> Date: Wed, 22 Aug 2012 06:23:01 -0700 From: Arjan van de Ven User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:14.0) Gecko/20120713 Thunderbird/14.0 MIME-Version: 1.0 To: Matthew Garrett CC: Mike Galbraith , Alan Cox , Ingo Molnar , Peter Zijlstra , Alex Shi , Suresh Siddha , vincent.guittot@linaro.org, svaidy@linux.vnet.ibm.com, Andrew Morton , Linus Torvalds , "linux-kernel@vger.kernel.org" , Thomas Gleixner , Paul Turner Subject: Re: [discussion]sched: a rough proposal to enable power saving in scheduler References: <1345043096.31459.106.camel@twins> <502BE38D.9030405@linux.intel.com> <20120820080606.GA6931@gmail.com> <20120820181651.GA737@srcf.ucam.org> <20120821094203.GB12385@gmail.com> <20120821113951.GA22436@srcf.ucam.org> <20120821151910.GA5359@gmail.com> <20120821170254.0b10ece6@pyramind.ukuu.org.uk> <1345614110.4374.65.camel@marge.simpson.net> <5034D878.1000305@linux.intel.com> <20120822132105.GA21852@srcf.ucam.org> In-Reply-To: <20120822132105.GA21852@srcf.ucam.org> X-Enigmail-Version: 1.4.3 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1225 Lines: 25 On 8/22/2012 6:21 AM, Matthew Garrett wrote: > On Wed, Aug 22, 2012 at 06:02:48AM -0700, Arjan van de Ven wrote: >> On 8/21/2012 10:41 PM, Mike Galbraith wrote: >>> For my dinky dual core laptop, I suspect you're right, but for a more >>> powerful laptop, I'd expect spread/don't to be noticeable. >> >> yeah if you don't spread, you will waste some power. >> but.. current linux behavior is to spread. >> so we can only make it worse. > > Right. For a single socket system the only thing you can do is use two > threads in preference to using two cores. That'll keep an extra core in > a deep C state for longer, at the cost of keeping the package out of a > deep C state for longer. There might be a win if the two processes > benefit from improved L1 cache locality, or if you're talking about basically "if HT sharing would be good for performance" ;-) (btw this is good news, it means this is not an actual power/performance tradeoff, but a "get it right" tradeoff) -- 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/