From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755561AbZBZI7G (ORCPT ); Thu, 26 Feb 2009 03:59:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753171AbZBZI6j (ORCPT ); Thu, 26 Feb 2009 03:58:39 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:37015 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752731AbZBZI6h (ORCPT ); Thu, 26 Feb 2009 03:58:37 -0500 Date: Thu, 26 Feb 2009 14:28:31 +0530 From: Dipankar Sarma To: Ingo Molnar 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: <20090226085831.GA28397@in.ibm.com> Reply-To: dipankar@in.ibm.com References: <20090220132145.GF26418@elte.hu> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090223110725.GB17312@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks Dipankar