From patchwork Mon Jun 21 18:49:23 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 12335501 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 86B04C48BE5 for ; Mon, 21 Jun 2021 18:50:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 69C1E60FEE for ; Mon, 21 Jun 2021 18:50:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232513AbhFUSwT (ORCPT ); Mon, 21 Jun 2021 14:52:19 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:43864 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231837AbhFUSwN (ORCPT ); Mon, 21 Jun 2021 14:52:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624301398; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:in-reply-to:in-reply-to:references:references; bh=swO++E6Xe5gmahVfon/2vkT+NXylz10k5vVf6UUkIHE=; b=WSBiPyUKJsDfJ7GbXLYBZ8aA4dC94ERGMhfxUFme7xMBCepD11MNWAWpaqluvcGA4X+3fg vL9H47ArfHB3AHnXHQFElTWzQkq4/nAzL1xMr46J97F7BhXKJe7xJnSXko4NNwmzzbgFY9 GaPvGiOEiMjs3zsdxSbsNFkTIkIZbK4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-478-rg8wNIO_PcWWY9qwCK676w-1; Mon, 21 Jun 2021 14:49:55 -0400 X-MC-Unique: rg8wNIO_PcWWY9qwCK676w-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 43483800D55; Mon, 21 Jun 2021 18:49:53 +0000 (UTC) Received: from llong.com (ovpn-114-127.rdu2.redhat.com [10.10.114.127]) by smtp.corp.redhat.com (Postfix) with ESMTP id EE8B75D9CA; Mon, 21 Jun 2021 18:49:51 +0000 (UTC) From: Waiman Long To: Tejun Heo , Zefan Li , Johannes Weiner , Jonathan Corbet , Shuah Khan Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Morton , Roman Gushchin , Phil Auld , Peter Zijlstra , Juri Lelli , Waiman Long Subject: [PATCH v2 5/6] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Date: Mon, 21 Jun 2021 14:49:23 -0400 Message-Id: <20210621184924.27493-6-longman@redhat.com> In-Reply-To: <20210621184924.27493-1-longman@redhat.com> References: <20210621184924.27493-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Update Documentation/admin-guide/cgroup-v2.rst on the newly introduced "isolated" cpuset partition type as well as the ability to create non-top cpuset partition with no cpu allocated to it. Signed-off-by: Waiman Long --- Documentation/admin-guide/cgroup-v2.rst | 65 +++++++++++++++++-------- 1 file changed, 44 insertions(+), 21 deletions(-) diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index b1e81aa8598a..cf40a7f499c0 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -2010,8 +2010,9 @@ Cpuset Interface Files It accepts only the following input values when written to. ======== ================================ - "root" a partition root - "member" a non-root member of a partition + "member" Non-root member of a partition + "root" Partition root + "isolated" Partition root without load balancing ======== ================================ When set to be a partition root, the current cgroup is the @@ -2020,6 +2021,11 @@ Cpuset Interface Files partition roots themselves and their descendants. The root cgroup is always a partition root. + With "isolated", the CPUs in that partition root will be in an + isolated state without any load balancing from the scheduler. + Tasks in such a partition must be explicitly bind to each + individual CPU. + There are constraints on where a partition root can be set. It can only be set in a cgroup if all the following conditions are true. @@ -2038,12 +2044,25 @@ Cpuset Interface Files file cannot be reverted back to "member" 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. + A parent partition may distribute all its CPUs to its child + partitions as long as it is not the root cgroup and there is no + task directly associated with that parent partition. Otherwise, + there must be at least one cpu left in the parent partition. + A new task cannot be moved to a partition root with no effective + cpu. Once becoming a partition root, changes to "cpuset.cpus" is - generally allowed as long as the first condition above is true, + generally allowed as long as the first condition above is true. + Other constraints for this operation are as follows. + + 1) Any newly added CPUs must be a subset of the parent's + "cpuset.cpus.effective". + 2) Taking away all the CPUs from the parent's "cpuset.cpus.effective" + is only allowed if there is no task associated with the + parent partition. + 3) Deletion of CPUs that have been distributed to child partition + roots are not allowed. + 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. @@ -2056,6 +2075,7 @@ Cpuset Interface Files ============== ============================== "member" Non-root member of a partition "root" Partition root + "isolated" Partition root without load balancing "root invalid" Invalid partition root ============== ============================== @@ -2063,21 +2083,24 @@ Cpuset Interface Files above are true and at least one CPU from "cpuset.cpus" is granted by the parent cgroup. - A partition root can become invalid 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 itself. In this - case, it is not a real partition even though the restriction - of the first partition root condition above will still apply. - The cpu affinity of all the tasks in the cgroup will then be - associated with CPUs in the nearest ancestor partition. - - An invalid 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 cpu - affinity of all the tasks in the formerly invalid partition - will be associated to the CPUs of the newly formed partition. - Changing the partition state of an invalid partition root to - "member" is always allowed even if child cpusets are present. + A partition root becomes invalid if all the CPUs requested in + "cpuset.cpus" become unavailable. This can happen if all the + CPUs have been offlined, or the state of an ancestor partition + root become invalid. In this case, it is not a real partition + even though the restriction of the first partition root condition + above will still apply. The cpu affinity of all the tasks in + the cgroup will then be associated with CPUs in the nearest + ancestor partition. In the special case of a parent partition + competing with a child partition for the only CPU left, the + parent partition wins and the child partition becomes invalid. + + An invalid partition root can be transitioned back to a real + partition root if at least one of the requested CPUs become + available again. In this case, the cpu affinity of all the + tasks in the formerly invalid partition will be associated to + the CPUs of the newly formed partition. Changing the partition + state of an invalid partition root to "member" is always allowed + even if child cpusets are present. Device controller