From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 159C87DF8D for ; Wed, 23 May 2018 20:19:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934862AbeEWUS7 (ORCPT ); Wed, 23 May 2018 16:18:59 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:42094 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934873AbeEWUS5 (ORCPT ); Wed, 23 May 2018 16:18:57 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4569F4023112; Wed, 23 May 2018 20:18:56 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-182.bos.redhat.com [10.18.17.182]) by smtp.corp.redhat.com (Postfix) with ESMTP id 96E1D2166BB2; Wed, 23 May 2018 20:18:53 +0000 (UTC) Subject: Re: [PATCH v8 4/6] cpuset: Make generate_sched_domains() recognize isolated_cpus To: Patrick Bellasi Cc: Tejun Heo , Li Zefan , Johannes Weiner , Peter Zijlstra , Ingo Molnar , 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 References: <1526590545-3350-1-git-send-email-longman@redhat.com> <1526590545-3350-5-git-send-email-longman@redhat.com> <20180523173453.GY30654@e110439-lin> From: Waiman Long Organization: Red Hat Message-ID: Date: Wed, 23 May 2018 16:18:53 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180523173453.GY30654@e110439-lin> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Wed, 23 May 2018 20:18:56 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Wed, 23 May 2018 20:18:56 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'longman@redhat.com' RCPT:'' Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 05/23/2018 01:34 PM, Patrick Bellasi wrote: > Hi Waiman, > > On 17-May 16:55, Waiman Long wrote: > > [...] > >> @@ -672,13 +672,14 @@ static int generate_sched_domains(cpumask_var_t **domains, >> int ndoms = 0; /* number of sched domains in result */ >> int nslot; /* next empty doms[] struct cpumask slot */ >> struct cgroup_subsys_state *pos_css; >> + bool root_load_balance = is_sched_load_balance(&top_cpuset); >> >> doms = NULL; >> dattr = NULL; >> csa = NULL; >> >> /* Special case for the 99% of systems with one, full, sched domain */ >> - if (is_sched_load_balance(&top_cpuset)) { >> + if (root_load_balance && !top_cpuset.isolation_count) { > Perhaps I'm missing something but, it seems to me that, when the two > conditions above are true, then we are going to destroy and rebuild > the exact same scheduling domains. > > IOW, on 99% of systems where: > > is_sched_load_balance(&top_cpuset) > top_cpuset.isolation_count = 0 > > since boot time and forever, then every time we update a value for > cpuset.cpus we keep rebuilding the same SDs. > > It's not strictly related to this patch, the same already happens in > mainline based just on the first condition, but since you are extending > that optimization, perhaps you can tell me where I'm possibly wrong or > which cases I'm not considering. > > I'm interested mainly because on Android systems those conditions > are always true and we see SDs rebuilds every time we write > something in cpuset.cpus, which ultimately accounts for almost all the > 6-7[ms] time required for the write to return, depending on the CPU > frequency. > > Cheers Patrick > Yes, that is true. I will look into how to further optimize this. Thanks for the suggestion. -Longman -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html