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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 83ACCC432C3 for ; Fri, 15 Nov 2019 17:18:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5956820732 for ; Fri, 15 Nov 2019 17:18:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727606AbfKORSL (ORCPT ); Fri, 15 Nov 2019 12:18:11 -0500 Received: from mx2.suse.de ([195.135.220.15]:46116 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727531AbfKORSL (ORCPT ); Fri, 15 Nov 2019 12:18:11 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 367BDAD20; Fri, 15 Nov 2019 17:18:09 +0000 (UTC) Date: Fri, 15 Nov 2019 18:18:07 +0100 From: Michal =?iso-8859-1?Q?Koutn=FD?= To: Valentin Schneider Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, lizefan@huawei.com, tj@kernel.org, hannes@cmpxchg.org, mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, Dietmar.Eggemann@arm.com, morten.rasmussen@arm.com, qperret@google.com Subject: Re: [PATCH v2] sched/topology, cpuset: Account for housekeeping CPUs to avoid empty cpumasks Message-ID: <20191115171807.GH19372@blackbody.suse.cz> References: <20191104003906.31476-1-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="nFBW6CQlri5Qm8JQ" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --nFBW6CQlri5Qm8JQ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello. On Thu, Nov 14, 2019 at 04:03:50PM +0000, Valentin Schneider wrote: > Michal, could I nag you for a reviewed-by? I'd feel a bit more confident > with any sort of approval from folks who actually do use cpusets. TL;DR I played with the v5.4-rc6 _without_ this fixup and I conclude it unnecessary (IOW my previous theoretical observation was wrong). The original problem is non-issue with v2 cpuset controller, because effective_cpus are never empty. isolcpus doesn't take out cpuset CPUs, hotplug does. In the case, no online CPU remains in the cpuset, it inherits ancestor's non-empty cpuset. I reproduced the problem with v1 (before your fix). However, in v1 effective =3D=3D allowed (we're destructive and overwrite allowed on hotunplug) and we already check the emptiness of=20 cpumask_intersects(cp->cpus_allowed, housekeeping_cpumask(HK_FLAG_DOMAIN) few lines higher. I.e. the fixup adds redundant check against the empty sched domain production. Sorry for the noise and HTH, Michal --nFBW6CQlri5Qm8JQ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEEoQaUCWq8F2Id1tNia1+riC5qSgFAl3O3cgACgkQia1+riC5 qSiGeA//dbxeLleRivvTRMu6ewhKeYA5GfAfmrsle+ZHgxKgu13LIa8eHLAWPu/Z YyHPHLctNpNYafHe47dMbAxduA4roPTtZzN8AMN4bRkrT85c1ZqCAVel6eZLU9Dj RIwV9vK3E6RBObG8W9Qq7b6Rhlty6mwnGpxil7oqJq/MxKe0DOYjYKsrl5JROc3G iywiIignt9izFFqK1z7R4TX4H9Q0ir/FEiu75CWMx7Ch5jSMgCUwcJiE1gTDognS vKIDIp0BD4nidnpLoP18iaywle6HbZOX6xT2GJXS5waCY6uKzHas++Jh/PdWYpTR +fzCQDS9otWlwSPUj/GSKwJbRakmxMWsfJp2/QreiWWbcS9XBxEH56jD03PBIF8A 3toQN5kLVu+kWf2v5v+avd6jaIXMRtm5uBigmkmmax/vjq9UtzWI8FzMhcx48BTI FHzWdwP3BcptZClp6O/4pLQ8doP/RINGtQgvYvnFvEDrJQGO2xxJ78FBRZ7WxQVU BuS3yDu8Ntxa8CuJBgFNJpN9yDu0rGHbknKDTHZ2vXWT6/v6B3B2UkdGGvmm4mQC RKoUjKoTQoLDCIvErQLI+PP62twGsz0lGJVm8WEPhVbs5AZIXPAJ8tx8LKngfXE8 38cy25tQ+hKhVtf+jIclTTYaN3Nvh2MBUKpZYXAQwdvXeiGn3NI= =2oDh -----END PGP SIGNATURE----- --nFBW6CQlri5Qm8JQ--