Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752403AbbB0Jcm (ORCPT ); Fri, 27 Feb 2015 04:32:42 -0500 Received: from casper.infradead.org ([85.118.1.10]:33952 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751232AbbB0Jck (ORCPT ); Fri, 27 Feb 2015 04:32:40 -0500 Date: Fri, 27 Feb 2015 10:32:31 +0100 From: Peter Zijlstra To: riel@redhat.com Cc: linux-kernel@vger.kernel.org, Clark Williams , Li Zefan , Ingo Molnar , Luiz Capitulino , Mike Galbraith , cgroups@vger.kernel.org Subject: Re: [PATCH 1/2] cpusets,isolcpus: exclude isolcpus from load balancing in cpusets Message-ID: <20150227093231.GG21418@twins.programming.kicks-ass.net> References: <1424882288-2910-1-git-send-email-riel@redhat.com> <1424882288-2910-2-git-send-email-riel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1424882288-2910-2-git-send-email-riel@redhat.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1764 Lines: 41 On Wed, Feb 25, 2015 at 11:38:07AM -0500, riel@redhat.com wrote: > From: Rik van Riel > > Ensure that cpus specified with the isolcpus= boot commandline > option stay outside of the load balancing in the kernel scheduler. > > Operations like load balancing can introduce unwanted latencies, > which is exactly what the isolcpus= commandline is there to prevent. > > Previously, simply creating a new cpuset, without even touching the > cpuset.cpus field inside the new cpuset, would undo the effects of > isolcpus=, by creating a scheduler domain spanning the whole system, > and setting up load balancing inside that domain. The cpuset root > cpuset.cpus file is read-only, so there was not even a way to undo > that effect. > > This does not impact the majority of cpusets users, since isolcpus= > is a fairly specialized feature used for realtime purposes. > > Cc: Peter Zijlstra > Cc: Clark Williams > Cc: Li Zefan > Cc: Ingo Molnar > Cc: Luiz Capitulino > Cc: Mike Galbraith > Cc: cgroups@vger.kernel.org > Signed-off-by: Rik van Riel > Tested-by: David Rientjes Might I asked you to update Documentation/cgroups/cpusets.txt with this knowledge? While it does mentions isolcpus it does not clarify the interaction between it and cpusets. Other than that, Acked-by: Peter Zijlstra (Intel) -- 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/