From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753327Ab1IXDHZ (ORCPT ); Fri, 23 Sep 2011 23:07:25 -0400 Received: from mail-pz0-f42.google.com ([209.85.210.42]:56515 "EHLO mail-pz0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753140Ab1IXDHY (ORCPT ); Fri, 23 Sep 2011 23:07:24 -0400 Date: Sat, 24 Sep 2011 12:07:18 +0900 From: Tejun Heo To: Gilad Ben-Yossef Cc: Ripduman Sohan , linux-kernel@vger.kernel.org, peterz@infradead.org Subject: Re: [PATCH] workqueue: Restore cpus_allowed mask for sleeping workqueue rescue threads Message-ID: <20110924030718.GA29319@htj.dyndns.org> References: <1314884193-20454-1-git-send-email-ripduman.sohan@cl.cam.ac.uk> <20110902002917.GD2752@htj.dyndns.org> <20110915161430.GE1548@tusker> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Sun, Sep 18, 2011 at 09:36:57AM +0300, Gilad Ben-Yossef wrote: > There is at least one use case where I think this can be a problem - > cpu isolation. > > If you decide to partition your CPU to give some group of processes a > set of CPUs all to their own (using cgroups/cpuset for example) having > non related bound processes really gets in the way. You would really > want to migrate away non related tasks from the isolated cpuset and > having a bound kernel thread prevents that. Hmm... I don't think this has much to do with CPU isolation. Workqueue rescuers are reactively invoked to resolve possible resource deadlock. It doesn't initiate operations on itself while CPU isolation requires moving all sources of unwanted activites off the isolated CPUs. Having idle rescuers not bound to any CPU might look prettier but wouldn't help anything - it's not an activity source and the 'wanted' activities on the isolated CPU also require rescuers for forward progress guarantee. Thanks. -- tejun