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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C9B3C77B78 for ; Tue, 2 May 2023 22:27:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229772AbjEBW1a (ORCPT ); Tue, 2 May 2023 18:27:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50960 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229457AbjEBW13 (ORCPT ); Tue, 2 May 2023 18:27:29 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C5E010E7; Tue, 2 May 2023 15:27:27 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 58A8B21F42; Tue, 2 May 2023 22:27:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1683066446; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VYMMl6QukjJ+AWKIxzwYKmP/x77nkL2kqwU3yC0/IAE=; b=twfR7/D1Mak2ce6QwCqeTdus/uNI/7WRnQBvtx+NzXxn0Fj5eKkbNVZAK7QhBvYLti8zL7 AiNmE4199XoBMBtHzSn9dcoznncO9bmqgACe9SnzsjqwNTuCORcM6MUay4wJbyzTFM6rvZ bqUL4+t/6cqzpUiWOZiSFZkM3NHvDmY= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 0DB9C134FB; Tue, 2 May 2023 22:27:26 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id IwtUAk6OUWTwYgAAMHmgww (envelope-from ); Tue, 02 May 2023 22:27:26 +0000 Date: Wed, 3 May 2023 00:27:24 +0200 From: Michal =?iso-8859-1?Q?Koutn=FD?= To: Waiman Long Cc: Tejun Heo , Zefan Li , Johannes Weiner , Jonathan Corbet , Shuah Khan , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Juri Lelli , Valentin Schneider , Frederic Weisbecker Subject: Re: [RFC PATCH 0/5] cgroup/cpuset: A new "isolcpus" paritition Message-ID: References: <9862da55-5f41-24c3-f3bb-4045ccf24b2e@redhat.com> <226cb2da-e800-6531-4e57-cbf991022477@redhat.com> <60ec12dc-943c-b8f0-8b6f-97c5d332144c@redhat.com> <46d26abf-a725-b924-47fa-4419b20bbc02@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Tue, May 02, 2023 at 05:26:17PM -0400, Waiman Long = wrote: > In the new scheme, the available cpus are still directly passed down to a > descendant cgroup. However, isolated CPUs (or more generally CPUs dedicat= ed > to a partition) have to be exclusive. So what the cpuset.cpus.reserve does > is to identify those exclusive CPUs that can be excluded from the > effective_cpus of the parent cgroups before they are claimed by a child > partition. Currently this is done automatically when a child partition is > created off a parent partition root. The new scheme will break it into 2 > separate steps without the requirement that the parent of a partition has= to > be a partition root itself. new scheme 1st step: echo C >p/cpuset.cpus.reserve # p/cpuset.cpus.effective =3D=3D A-C (1) 2nd step (claim): echo C' >p/c/cpuset.cpus # C'=E2=8A=86C echo root >p/c/cpuset.cpus.partition current scheme 1st step (configure): echo C >p/c/cpuset.cpus 2nd step (reserve & claim): echo root >p/c/cpuset.cpus.partition # p/cpuset.cpus.effective =3D=3D A-C (2) As long as p/c is unpopulated, (1) and (2) are equal situations. Why is the (different) two step procedure needed? Also the relaxation of requirement of a parent being a partition confuses me -- if the parent is not a partition, i.e. it has no exclusive ownership of CPUs but it can still "give" it to children -- is child partition meant to be exclusive? (IOW can parent siblings reserve some same CPUs?) Thanks, Michal