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=-9.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 66108C64E7A for ; Tue, 1 Dec 2020 22:32:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 047BE208DB for ; Tue, 1 Dec 2020 22:31:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="i8yPkW/j" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726026AbgLAWbo (ORCPT ); Tue, 1 Dec 2020 17:31:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:38942 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727209AbgLAWbn (ORCPT ); Tue, 1 Dec 2020 17:31:43 -0500 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 368C720671; Tue, 1 Dec 2020 22:31:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606861863; bh=2FqELP0kL1gtJg1OgZdi1DE1pZCr06wueem7RmEe9ew=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=i8yPkW/jGk0Rof1aFRSlnu+HT5bXjtUslWWaorpHYJtwOfdMUAEKVlXWk5mrLwBlV n/4S/aYvK9qw5fHqyP4PTFSaiolKLTqGugnZYxJ9lF1kEPS57nonNGG6my5fRrQZYe ycm/49bt3VYwv3FRSYWh0IJzJDSYaWy/82K87u5w= Date: Tue, 1 Dec 2020 22:30:56 +0000 From: Will Deacon To: Quentin Perret Cc: Qais Yousef , linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Catalin Marinas , Marc Zyngier , Greg Kroah-Hartman , Peter Zijlstra , Morten Rasmussen , Suren Baghdasaryan , Tejun Heo , Li Zefan , Johannes Weiner , Ingo Molnar , Juri Lelli , Vincent Guittot , kernel-team@android.com Subject: Re: [PATCH v4 09/14] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Message-ID: <20201201223056.GB28496@willie-the-truck> References: <20201124155039.13804-1-will@kernel.org> <20201124155039.13804-10-will@kernel.org> <20201127133245.4hbx65mo3zinawvo@e107158-lin.cambridge.arm.com> <20201130170531.qo67rai5lftskmk2@e107158-lin.cambridge.arm.com> <20201130173610.GA1715200@google.com> <20201201115842.t77abecneuesd5ih@e107158-lin.cambridge.arm.com> <20201201123748.GA1896574@google.com> <20201201141121.5w2wed3633slo6dw@e107158-lin.cambridge.arm.com> <20201201155649.GB1914005@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201201155649.GB1914005@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Tue, Dec 01, 2020 at 03:56:49PM +0000, Quentin Perret wrote: > On Tuesday 01 Dec 2020 at 14:11:21 (+0000), Qais Yousef wrote: > > For cpusets, if hotunplug results in an empty cpuset, then all tasks are moved > > to the nearest ancestor if I read the code correctly. In our case, only 32bit > > tasks have to move out to retain this behavior. Since now for the first time we > > have tasks that can't run on all cpus. > > > > Which by the way might be the right behavior for 64bit tasks execing 32bit > > binary in a 64bit only cpuset. I suggested SIGKILL'ing them but maybe moving > > them to the nearest ancestor too is more aligned with the behavior above. > > Hmm, I guess that means putting all 32-bit-execd-from-64-bit tasks in > the root group in Android. I'll try and check the implications, but that > might be just fine... Sounds like a sensible behaviour to me anyways. I'll look into this -- anything we can do to avoid forcefully resetting the affinity mask to the arch_task_cpu_possible_mask() is worth considering. Will