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=-13.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 683B0C4361B for ; Thu, 17 Dec 2020 13:45:44 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 28F70233E2 for ; Thu, 17 Dec 2020 13:45:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 28F70233E2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=j6nh20eJJUu44gEAB1p2xqTKB0kmvAxltsxTlXrEQ5A=; b=sQS/b7+tqKxV4wiZNq3yZVZNB upAuh48ylonYFMXtKTMKcP+dbO+ZDvy3pTW+c0H7s3jex7X0rwbgnnQ2wkwz9LBp1icRWf7G9XDL0 kf4LXCKzH/wIA0H4MDhbWcNjA5s+8R2/NZMEEobc8DM0NTwnhvbVw+ge6tto7LTrHbI1Z4SCNxK5a LJ5LKA3RC1ASO+wVQYnyRu9LlPOASzPsIPvs8cxB/XTdHT99Av4NTxOWgoGrxKBBOhIcK8utsdG+t 2MtdLuyxY6xz6JCun7iVu56wLSlQJ3VypjyvgTROp3sx74mQijLCF5eE6RwYsUEr4JJG+JxZu9GkZ Ig6ccx0Ew==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kptZg-0002Y5-2A; Thu, 17 Dec 2020 13:44:08 +0000 Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kptZb-0002Xs-Og; Thu, 17 Dec 2020 13:44:04 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BC09F305C11; Thu, 17 Dec 2020 14:44:01 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id AA07F201272D1; Thu, 17 Dec 2020 14:44:01 +0100 (CET) Date: Thu, 17 Dec 2020 14:44:01 +0100 From: Peter Zijlstra To: Qais Yousef Subject: Re: [PATCH v5 07/15] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Message-ID: <20201217134401.GY3040@hirez.programming.kicks-ass.net> References: <20201208132835.6151-1-will@kernel.org> <20201208132835.6151-8-will@kernel.org> <20201217121552.ds7g2icvqp5nvtha@e107158-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201217121552.ds7g2icvqp5nvtha@e107158-lin.cambridge.arm.com> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Juri Lelli , kernel-team@android.com, Vincent Guittot , Ingo Molnar , Greg Kroah-Hartman , Catalin Marinas , Quentin Perret , linux-kernel@vger.kernel.org, Suren Baghdasaryan , Johannes Weiner , Li Zefan , Marc Zyngier , Tejun Heo , Will Deacon , Morten Rasmussen , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Dec 17, 2020 at 12:15:52PM +0000, Qais Yousef wrote: > On 12/08/20 13:28, Will Deacon wrote: > > If the scheduler cannot find an allowed CPU for a task, > > cpuset_cpus_allowed_fallback() will widen the affinity to cpu_possible_mask > > if cgroup v1 is in use. > > > > In preparation for allowing architectures to provide their own fallback > > mask, just return early if we're not using cgroup v2 and allow > > select_fallback_rq() to figure out the mask by itself. > > > > Cc: Li Zefan > > Cc: Tejun Heo > > Cc: Johannes Weiner > > Reviewed-by: Quentin Perret > > Signed-off-by: Will Deacon > > --- > > kernel/cgroup/cpuset.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > > index 57b5b5d0a5fd..e970737c3ed2 100644 > > --- a/kernel/cgroup/cpuset.c > > +++ b/kernel/cgroup/cpuset.c > > @@ -3299,9 +3299,11 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) > > > > void cpuset_cpus_allowed_fallback(struct task_struct *tsk) > > { > > + if (!is_in_v2_mode()) > > + return; /* select_fallback_rq will try harder */ > > + > > rcu_read_lock(); > > - do_set_cpus_allowed(tsk, is_in_v2_mode() ? > > - task_cs(tsk)->cpus_allowed : cpu_possible_mask); > > + do_set_cpus_allowed(tsk, task_cs(tsk)->cpus_allowed); > > Why is it safe to return that for cpuset v2? v1 Because in that case it does cpu_possible_mask, which, if you look at select_fallback_rq(), is exactly what happens when cpuset 'fails' to find a candidate. Or at least, that's how I read the patch. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel