Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754817AbbB0RIj (ORCPT ); Fri, 27 Feb 2015 12:08:39 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39426 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752247AbbB0RIh (ORCPT ); Fri, 27 Feb 2015 12:08:37 -0500 Date: Fri, 27 Feb 2015 12:08:03 -0500 From: Rik van Riel To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Clark Williams , Li Zefan , Ingo Molnar , Luiz Capitulino , Mike Galbraith , cgroups@vger.kernel.org Subject: [PATCH 3/2] cpusets,isolcpus: document relationship between cpusets & isolcpus Message-ID: <20150227120803.07db15fe@annuminas.surriel.com> In-Reply-To: <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> <20150227093231.GG21418@twins.programming.kicks-ass.net> Organization: Red Hat, Inc. MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2016 Lines: 42 Document the subtly changed relationship between cpusets and isolcpus. Turns out the old documentation did not quite match the code... Signed-off-by: Rik van Riel Suggested-by: Peter Zijlstra --- Documentation/cgroups/cpusets.txt | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/Documentation/cgroups/cpusets.txt b/Documentation/cgroups/cpusets.txt index f2235a162529..fdf7dff3f607 100644 --- a/Documentation/cgroups/cpusets.txt +++ b/Documentation/cgroups/cpusets.txt @@ -392,8 +392,10 @@ Put simply, it costs less to balance between two smaller sched domains than one big one, but doing so means that overloads in one of the two domains won't be load balanced to the other one. -By default, there is one sched domain covering all CPUs, except those -marked isolated using the kernel boot time "isolcpus=" argument. +By default, there is one sched domain covering all CPUs, including those +marked isolated using the kernel boot time "isolcpus=" argument. However, +the isolated CPUs will not participate in load balancing, and will not +have tasks running on them unless explicitly assigned. This default load balancing across all CPUs is not well suited for the following two situations: @@ -465,6 +467,10 @@ such partially load balanced cpusets, as they may be artificially constrained to some subset of the CPUs allowed to them, for lack of load balancing to the other CPUs. +CPUs in "cpuset.isolcpus" were excluded from load balancing by the +isolcpus= kernel boot option, and will never be load balanced regardless +of the value of "cpuset.sched_load_balance" in any cpuset. + 1.7.1 sched_load_balance implementation details. ------------------------------------------------ -- 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/