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 59F2FC433FE for ; Tue, 31 May 2022 14:21:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345197AbiEaOVX (ORCPT ); Tue, 31 May 2022 10:21:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233327AbiEaOVW (ORCPT ); Tue, 31 May 2022 10:21:22 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C6C2170371 for ; Tue, 31 May 2022 07:21:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1654006878; 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=054tb8AogR5kqRpkgYxu+jA4/lLcTMkATpeGkVLSWIc=; b=Hl4m0BMnQzMusX6/hU2CKokGaBnOO97r8YUlBT0ACktb0zhErNfolKMk0hXddDLb3OLTOJ HMOxuk42dlwj9IeIxhQUqyuzUmiVVMfRZ8AUag4IlT45pr92Z3DwJIeGTKotaWcSqwMM8n asY7NJvHMXG8OG4qkQ5cfOWqRMmlDmE= 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-661-EylW6zkhOaC9wANYEmdqPg-1; Tue, 31 May 2022 10:21:12 -0400 X-MC-Unique: EylW6zkhOaC9wANYEmdqPg-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id CAE191C16B49; Tue, 31 May 2022 14:21:04 +0000 (UTC) Received: from [10.18.17.215] (dhcp-17-215.bos.redhat.com [10.18.17.215]) by smtp.corp.redhat.com (Postfix) with ESMTP id 09D20492CA2; Tue, 31 May 2022 14:21:04 +0000 (UTC) Message-ID: <6936d198-7ae4-e022-20d5-e60c17f119e8@redhat.com> Date: Tue, 31 May 2022 10:21:03 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [RFC PATCH 4/4] cpuset: Support RCU-NOCB toggle on v2 root partitions Content-Language: en-US To: Peter Zijlstra , Frederic Weisbecker Cc: Juri Lelli , Tejun Heo , LKML , "Paul E . McKenney" , Paul Gortmaker , Johannes Weiner , Marcelo Tosatti , Phil Auld , Zefan Li , Daniel Bristot de Oliveira , Nicolas Saenz Julienne , rcu@vger.kernel.org References: <20220526225141.GA1214445@lothringen> <9e44bb00-955a-dbc6-a863-be649e0c701f@redhat.com> <20220527083018.n43nc73vuuzm5ixo@localhost.localdomain> <20220530004049.GA1251147@lothringen> <20220530105650.GA1257179@lothringen> From: Waiman Long In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On 5/30/22 09:16, Peter Zijlstra wrote: > On Mon, May 30, 2022 at 12:56:50PM +0200, Frederic Weisbecker wrote: > >>> This is ABI, you can't walk back on it. I would suggest starting with an >>> 'all feature' isolation. Only if there's real demand for something more >>> fine-grained add that on top. Simple first etc. >> That's actually my worry. If we start with an all in one ABI, how do we later >> mix that up with more finegrained features? Like what will be the behaviour of: >> >> cpuset.isolation.rcu_nocb = 0 >> cpuset.isolation.all = 1 > Well clearly that doesn't make sense. I was more thinking along the > lines of cgroup.subtree_control, where instead all features are enabled > by default. > > But only if there's a real usecase, otherwise there's no point in > providing such knobs. I am actually thinking about extending the cpuset partition interface for isolation. Right now, I have an outstanding patch [1] to add an "isolated" state to partition which disable load balancing somewhat similar to isolcpus command line option. In the future, we can add attribute to the isolation state like "isolated:full" to similar to nohz_full currently. If the needs arise, we can even  extend the attribute to allow list like "isolated:rcu_nocbs". I don't think it is good idea to keep on adding new cpuset control files extensively. I would prefer extending the existing ones. [1] https://lore.kernel.org/lkml/20220510153413.400020-1-longman@redhat.com/ Cheers, Longman