Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752687AbYAVT2T (ORCPT ); Tue, 22 Jan 2008 14:28:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750843AbYAVT2H (ORCPT ); Tue, 22 Jan 2008 14:28:07 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:57349 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750821AbYAVT2G (ORCPT ); Tue, 22 Jan 2008 14:28:06 -0500 Date: Tue, 22 Jan 2008 20:27:44 +0100 From: Ingo Molnar To: Matt Mackall Cc: =?utf-8?B?Uy7Dh2HEn2xhcg==?= Onur , LKML , Arjan van de Ven Subject: Re: Rescheduling interrupts Message-ID: <20080122192744.GB3218@elte.hu> References: <200801220119.42312.caglar@pardus.org.tr> <200801221455.16814.caglar@pardus.org.tr> <20080122152333.GB19590@elte.hu> <200801221755.56470.caglar@pardus.org.tr> <20080122160557.GA31831@elte.hu> <1201021429.14436.45.camel@cinder.waste.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1201021429.14436.45.camel@cinder.waste.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1112 Lines: 24 * Matt Mackall wrote: > > amarokapp does wake up threads every 20 microseconds - that could > > explain it. It's probably Xorg running on one core, amarokapp on the > > other core. That's already 100 reschedules/sec. > > That suggests we want an "anti-load-balancing" heuristic when CPU > usage is very low. Migrating everything onto one core when we're close > to idle will save power and probably reduce latencies. that would probably be the case if it's multiple sockets - but for multiple cores exactly the opposite is true: the sooner _both_ cores finish processing, the deeper power use the CPU can reach. So effective and immediate spreading of workloads amongst multiple cores - especially with shared L2 caches where the cost of migration is low, helps power consumption. (and it obviously helps latencies and bandwith) Ingo -- 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/