Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755744Ab0GAMaM (ORCPT ); Thu, 1 Jul 2010 08:30:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:18251 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755438Ab0GAMaJ (ORCPT ); Thu, 1 Jul 2010 08:30:09 -0400 Date: Thu, 1 Jul 2010 15:23:40 +0300 From: "Michael S. Tsirkin" To: Peter Zijlstra Cc: Ingo Molnar , Sridhar Samudrala , Tejun Heo , Oleg Nesterov , netdev , lkml , "kvm@vger.kernel.org" , Andrew Morton , Dmitri Vorobiev , Jiri Kosina , Thomas Gleixner , Andi Kleen Subject: Re: [PATCH repost] sched: export sched_set/getaffinity to modules Message-ID: <20100701122340.GB31333@redhat.com> References: <4BFFE742.2060205@kernel.org> <20100530112925.GB27611@redhat.com> <4C02C99D.9070204@kernel.org> <20100624081135.GA937@redhat.com> <1277419551.27868.27.camel@w-sridhar.beaverton.ibm.com> <20100625101022.GA16321@redhat.com> <20100701110708.GA27368@redhat.com> <1277983179.1917.10.camel@laptop> <1277984603.1917.15.camel@laptop> <20100701115507.GA31333@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100701115507.GA31333@redhat.com> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1737 Lines: 46 On Thu, Jul 01, 2010 at 02:55:07PM +0300, Michael S. Tsirkin wrote: > On Thu, Jul 01, 2010 at 01:43:23PM +0200, Peter Zijlstra wrote: > > On Thu, 2010-07-01 at 13:19 +0200, Peter Zijlstra wrote: > > > On Thu, 2010-07-01 at 14:07 +0300, Michael S. Tsirkin wrote: > > > > Author: Sridhar Samudrala > > > > > > > > sched: export sched_set/getaffinity to modules > > > > > > > > vhost-net driver wants to copy the affinity from the > > > > owner thread to thread it creates. Export > > > > sched_set/get affinity to modules to make this possible > > > > when vhost is built as a module. > > > > > Urgh,.. so why again is that a good idea? > > > > In particular: > > - who sets the affinity of the task? > > management tools do this when they start qemu. > > > - why can't it set the kernel thread's affinity too? > > It can. However: the threads are started internally by the driver > when qemu does an ioctl. What we want to do is give it a sensible > default affinity. management tool can later tweak it if it wants to. > > > - what happens if someone changes the tasks' affinity? > > We would normally create a cgroup including all internal > tasks, making it easy to find and change affinity for > them all if necessary. > > > So no, I don't think this is a sensible thing to do at all. The patch using this is here: http://www.mail-archive.com/kvm@vger.kernel.org/msg35411.html It simply copies the affinity from the parent when thread is created. -- MST -- 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/