From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760184AbXFVRlu (ORCPT ); Fri, 22 Jun 2007 13:41:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758380AbXFVRll (ORCPT ); Fri, 22 Jun 2007 13:41:41 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:37096 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752933AbXFVRlk (ORCPT ); Fri, 22 Jun 2007 13:41:40 -0400 Date: Fri, 22 Jun 2007 10:41:38 -0700 From: Paul Jackson To: vatsa@linux.vnet.ibm.com Cc: mingo@elte.hu, clameter@sgi.com, linux-kernel@vger.kernel.org, dino@in.ibm.com, akpm@linux-foundation.org Subject: Re: cpuset attach_task to touch per-cpu kernel threads? Message-Id: <20070622104138.9c23e1f1.pj@sgi.com> In-Reply-To: <20070622171634.GA21543@linux.vnet.ibm.com> References: <20070621014935.GF10980@linux.vnet.ibm.com> <20070621121635.GB19811@elte.hu> <20070621100712.52a4784a.pj@sgi.com> <20070621173232.GP10980@linux.vnet.ibm.com> <20070621105152.8daf87ad.pj@sgi.com> <20070622171634.GA21543@linux.vnet.ibm.com> Organization: SGI X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.3; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Srivatsa wrote: > That again is not fool-proof. What if kernel-tasks change their cpu affinity > after we have done the is_pinned_kernel_thread() test? Ideally they > should not, but one never knows! > > IMHO we simply should not allow kernel threads to move out of top-cpuset Well ... in some theoretical world, perhaps. In reality, there a big pile of kernel threads that we want to move out of the root cpuset. And in reality, kernel threads don't change from being unrestricted (all cpus allowed) to being pinned (to some specific subset of cpus). Kernel threads that need to be pinned know it up front; it's an essential part of whatever they do. I've been working with installed customer configurations for about two and a half years now that move unpinned kernel threads out of the top cpuset, as part of keeping portions of the system freed up for dedicated jobs. I cannot agree to removing this capability. Nack. -- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson 1.925.600.0401