From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756042AbZBZPpz (ORCPT ); Thu, 26 Feb 2009 10:45:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753664AbZBZPpr (ORCPT ); Thu, 26 Feb 2009 10:45:47 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:38207 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753613AbZBZPpq (ORCPT ); Thu, 26 Feb 2009 10:45:46 -0500 Date: Thu, 26 Feb 2009 16:45:26 +0100 From: Ingo Molnar To: Dipankar Sarma Cc: Vaidyanathan Srinivasan , Balbir Singh , Arjan van de Ven , linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org, a.p.zijlstra@chello.nl, ego@in.ibm.com, tglx@linutronix.de, andi@firstfloor.org, venkatesh.pallipadi@intel.com, vatsa@linux.vnet.ibm.com, arun@linux.vnet.ibm.com, Suresh Siddha Subject: Re: [RFC PATCH 0/4] timers: framework for migration between CPU Message-ID: <20090226154526.GD352@elte.hu> References: <20090220141415.GA27381@dirshya.in.ibm.com> <20090220160737.GC11294@elte.hu> <20090220115745.43d202d6@infradead.org> <20090220215318.GA30665@elte.hu> <20090223075521.GA3725@balbir.in.ibm.com> <20090223091158.GJ9582@elte.hu> <20090223094850.GA10226@balbir.in.ibm.com> <20090223103814.GB8817@dirshya.in.ibm.com> <20090223110725.GB17312@elte.hu> <20090226085831.GA28397@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090226085831.GA28397@in.ibm.com> User-Agent: Mutt/1.5.18 (2008-05-17) 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 * Dipankar Sarma wrote: > On Mon, Feb 23, 2009 at 12:07:25PM +0100, Ingo Molnar wrote: > > > > * Vaidyanathan Srinivasan wrote: > > > > > * Identify set of idle CPUs (CPU package) from which timers > > > can be removed > > > * Identify a semi-idle or idle CPU package to which the timers > > > can be moved > > > * Decide when to start moving timers as the system has large > > > number of idle CPUs > > > * Decide when to stop migrating as system becomes less idle > > > and utilisation increases > > > > > > Guiding all of the above decisions from user space may not be > > > fast enough. > > > > Exactly. > > That is true for power management. However there are other > situations where we may need targeted avoidance of timers. > Certain type of applications - HPC for example - prefer > avoidance of jitters due to periodic timers. It would be good > to be able to say "avoid these CPUs for timers" while they are > being used for HPC tasks. Yes - but that kind of policy should be coupled and expressed via cpusets. /proc based irq_affinity is just a limited, inflexible hack. All things IRQ partitioning should be handled via cpusets - perhaps via the 'system sets' idea from Peter? Ingo