From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8389DC04AA5 for ; Mon, 15 Oct 2018 20:30:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5345D208B3 for ; Mon, 15 Oct 2018 20:30:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5345D208B3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727189AbeJPERk (ORCPT ); Tue, 16 Oct 2018 00:17:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48474 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726091AbeJPERk (ORCPT ); Tue, 16 Oct 2018 00:17:40 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C982430015CF; Mon, 15 Oct 2018 20:30:49 +0000 (UTC) Received: from llong.com (dhcp-17-8.bos.redhat.com [10.18.17.8]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2A665768AE; Mon, 15 Oct 2018 20:30:45 +0000 (UTC) From: Waiman Long To: Tejun Heo , Li Zefan , Johannes Weiner , Peter Zijlstra , Ingo Molnar Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, Mike Galbraith , torvalds@linux-foundation.org, Roman Gushchin , Juri Lelli , Patrick Bellasi , Tom Hromatka , Waiman Long Subject: [PATCH v14 10/12] cpuset: Add documentation about the new "cpuset.sched.partition" flag Date: Mon, 15 Oct 2018 16:29:35 -0400 Message-Id: <1539635377-22335-11-git-send-email-longman@redhat.com> In-Reply-To: <1539635377-22335-1-git-send-email-longman@redhat.com> References: <1539635377-22335-1-git-send-email-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Mon, 15 Oct 2018 20:30:50 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The cgroup-v2.rst file is updated to document the purpose of the new "cpuset.sched.partition" flag and how its usage. Signed-off-by: Waiman Long --- Documentation/admin-guide/cgroup-v2.rst | 66 +++++++++++++++++++++++++ 1 file changed, 66 insertions(+) diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 533e85cb851b..178cda473a26 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -1686,6 +1686,72 @@ Cpuset Interface Files Its value will be affected by memory nodes hotplug events. + cpuset.sched.partition + A read-write single value file which exists on non-root + cpuset-enabled cgroups. It accepts either "0" (off) or "1" + (on) when written to. This flag is set and owned by the + parent cgroup. + + If set, it indicates that the current cgroup is the root of a + new partition or scheduling domain that comprises itself and + all its descendants except those that are separate partition + roots themselves and their descendants. The root cgroup is + always a partition root. + + There are constraints on where this flag can be set. It can + only be set in a cgroup if all the following conditions are true. + + 1) The "cpuset.cpus" is not empty and the list of CPUs are + exclusive, i.e. they are not shared by any of its siblings. + 2) The parent cgroup is a partition root. + 3) The "cpuset.cpus" is also a proper subset of the parent's + "cpuset.cpus.effective". + 4) There is no child cgroups with cpuset enabled. This is for + eliminating corner cases that have to be handled if such a + condition is allowed. + + Setting this flag will take the CPUs away from the effective + CPUs of the parent cgroup. Once it is set, this flag cannot + be cleared if there are any child cgroups with cpuset enabled. + + A parent partition cannot distribute all its CPUs to its + child partitions. There must be at least one cpu left in the + parent partition. + + Once becoming a partition root, changes to "cpuset.cpus" is + generally allowed as long as the first condition above is true, + the change will not take away all the CPUs from the parent + partition and the new "cpuset.cpus" value is a superset of its + children's "cpuset.cpus" values. + + Sometimes, external factors like changes to ancestors' + "cpuset.cpus" or cpu hotplug can cause the state of the partition + root to change. On read, the "cpuset.sched.partition" file + can show the following values. + + "0" Not a partition root + "1" Partition root + "-1" Erroneous partition root + + It is a partition root if the first 2 partition root conditions + above are true and at least one CPU from "cpuset.cpus" is + granted by the parent cgroup. + + A partition root can become an erroneous partition root if none + of CPUs requested in "cpuset.cpus" can be granted by the parent + cgroup or the parent cgroup is no longer a partition root. + In this case, it is not a real partition even though the + restriction of the first partition root condition above will + still apply. All the tasks in the cgroup will be migrated to + the nearest ancestor partition. + + An erroneous partition root can be transitioned back to a real + partition root if at least one of the requested CPUs can now be + granted by its parent. In this case, the tasks will be migrated + back to the newly created partition. Clearing the partition + flag of an erroneous partition root is always allowed even if + child cpusets are present. + Device controller ----------------- -- 2.18.0