From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758950AbXHBTsl (ORCPT ); Thu, 2 Aug 2007 15:48:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758076AbXHBTsc (ORCPT ); Thu, 2 Aug 2007 15:48:32 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:46851 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758071AbXHBTsc (ORCPT ); Thu, 2 Aug 2007 15:48:32 -0400 Date: Thu, 2 Aug 2007 21:48:25 +0200 From: Ingo Molnar To: Martin Roehricht Cc: linux-kernel@vger.kernel.org Subject: Re: Scheduling the highest priority task Message-ID: <20070802194825.GA23245@elte.hu> References: <8KLFD-G9-5@gated-at.bofh.it> <46B19CA1.7050204@felicis.org> <20070802114012.GA4067@elte.hu> <46B1F182.3010608@felicis.org> <20070802150350.GA3030@elte.hu> <46B1F4BA.4010107@felicis.org> <20070802151916.GA8688@elte.hu> <46B1FC6D.7010202@felicis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <46B1FC6D.7010202@felicis.org> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: 1.0 X-ELTE-SpamLevel: s X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=1.0 required=5.9 tests=BAYES_50 autolearn=no SpamAssassin version=3.0.3 1.0 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.5053] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Martin Roehricht wrote: > On 08/02/2007 05:19 PM, Ingo Molnar wrote: > >* Martin Roehricht wrote: > > > >>That's fine with me, that within the same priority-queue any task can > >>be chosen. But assume two tasks with highly different priorities, such > >>as 105 and 135 are scheduled on the same processor and one of them is > >>now to be migrated -- shouldn't be the queue with task P=105 > >>considered first for migration by this code? Both tasks would use > >>different queues with their own linked lists, right? > > > >yes. What makes you believe that the lower priority one (prio 135) is > >chosen? [ as i said before, that will only be chosen if all tasks in the > >higher-priority queue (prio 105) are either already running on a CPU or > >have recently run so that the cache-hot logic skips them. ] > > This believe is primarily based on my observations of multiple > benchmark runs and also on your statement earlier: ģin the SMP > migration code, the 'old scheduler' indeed picks the lowest priority > oneĢ. oh, sorry, that was meant to be the 'highest priority one' :-/ so i think you got it all right, i just typoed that first sentence. Ingo