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 19630C04A68 for ; Thu, 28 Jul 2022 14:49:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230164AbiG1Ote (ORCPT ); Thu, 28 Jul 2022 10:49:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229704AbiG1Otb (ORCPT ); Thu, 28 Jul 2022 10:49:31 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1C26651413 for ; Thu, 28 Jul 2022 07:49:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1659019770; h=from:from:reply-to:subject:subject: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=Y72epJF5d8qli+9Ce0BVC/x2v9XQ9z23UFNcVj/FJ4A=; b=Fc8wIT1wXK1+SxUbIFbxzulBtkPLyuxLqHjQZLK+z2m4xY7ZV2VLKwaFIaQHZ+IOADuHLV ninCdV7+fLKPvFgpz0BHFBGzuMoSfFjBwfcCvaWqgL071utlAkrTDtBozMnnYOSjWNclVR qHEKerfUyM6taRzCEI4YoTWTLtZFfik= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-534-XijDdIi4PyCKyGWgOxNPkA-1; Thu, 28 Jul 2022 10:49:24 -0400 X-MC-Unique: XijDdIi4PyCKyGWgOxNPkA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 513D81C0BC6A; Thu, 28 Jul 2022 14:49:23 +0000 (UTC) Received: from [10.22.9.86] (unknown [10.22.9.86]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4854740CF8EB; Thu, 28 Jul 2022 14:49:22 +0000 (UTC) Message-ID: <8e0a41e6-8d03-b0ad-02b5-04449c49c470@redhat.com> Date: Thu, 28 Jul 2022 10:49:21 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH 2/2] cgroup: Skip subtree root in cgroup_update_dfl_csses() Content-Language: en-US To: =?UTF-8?Q?Michal_Koutn=c3=bd?= Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Tejun Heo , Zefan Li , Johannes Weiner , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org References: <20220728005815.1715522-1-longman@redhat.com> <20220728005815.1715522-2-longman@redhat.com> <20220728144426.GA26631@blackbody.suse.cz> From: Waiman Long In-Reply-To: <20220728144426.GA26631@blackbody.suse.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/28/22 10:44, Michal Koutný wrote: > On Wed, Jul 27, 2022 at 08:58:15PM -0400, Waiman Long wrote: >> The cgroup_update_dfl_csses() function updates css associations when a >> cgroup's subtree_control file is modified. Any changes made to a cgroup's >> subtree_control file, however, will only affect its descendants but not >> the cgroup itself. > I find this correct. > >> So there is no point in migrating csses associated with that cgroup. >> We can skip them instead. > Alone it's not such a big win but it componds with the recent Tejun's > threadgroup_rwsem elision. > It is more an optimization patch trying to not waste cpu time doing unnecessary work. >> --- >> kernel/cgroup/cgroup.c | 9 +++++++++ >> 1 file changed, 9 insertions(+) > Feel free to have > Reviewed-by: Michal Koutný > Thanks for the review. Cheers, Longman