From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757288AbbCCXA0 (ORCPT ); Tue, 3 Mar 2015 18:00:26 -0500 Received: from shelob.surriel.com ([74.92.59.67]:52024 "EHLO shelob.surriel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751941AbbCCXAZ (ORCPT ); Tue, 3 Mar 2015 18:00:25 -0500 From: riel@redhat.com To: tj@kernel.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH 4/4] cpuset,isolcpus: document relationship between cpusets & isolcpus Date: Tue, 3 Mar 2015 18:00:23 -0500 Message-Id: <1425423623-31316-5-git-send-email-riel@redhat.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1425423623-31316-1-git-send-email-riel@redhat.com> References: <1425423623-31316-1-git-send-email-riel@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rik van Riel Document the subtly changed relationship between cpusets and isolcpus. Turns out the old documentation did not 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. ------------------------------------------------ -- 2.1.0