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=-2.3 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 CDFD2C4CECE for ; Tue, 17 Sep 2019 09:54:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE0DF214AF for ; Tue, 17 Sep 2019 09:54:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727510AbfIQJyF (ORCPT ); Tue, 17 Sep 2019 05:54:05 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:2233 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726501AbfIQJyE (ORCPT ); Tue, 17 Sep 2019 05:54:04 -0400 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 4B34EC0AB5070CFC522D; Tue, 17 Sep 2019 17:54:01 +0800 (CST) Received: from [127.0.0.1] (10.74.191.121) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.439.0; Tue, 17 Sep 2019 17:53:58 +0800 Subject: Re: [PATCH v5] numa: make node_to_cpumask_map() NUMA_NO_NODE aware To: Michal Hocko CC: Michael Ellerman , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , References: <1568640481-133352-1-git-send-email-linyunsheng@huawei.com> <87pnjzsd8f.fsf@mpe.ellerman.id.au> <20190917093655.GA1872@dhcp22.suse.cz> From: Yunsheng Lin Message-ID: <07c78b6c-277e-eec0-a6cd-46beab1f1547@huawei.com> Date: Tue, 17 Sep 2019 17:53:57 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20190917093655.GA1872@dhcp22.suse.cz> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.74.191.121] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/9/17 17:36, Michal Hocko wrote: > On Tue 17-09-19 14:20:11, Yunsheng Lin wrote: >> On 2019/9/17 13:28, Michael Ellerman wrote: >>> Yunsheng Lin writes: > [...] >>>> But we cannot really copy the page allocator logic. Simply because the >>>> page allocator doesn't enforce the near node affinity. It just picks it >>>> up as a preferred node but then it is free to fallback to any other numa >>>> node. This is not the case here and node_to_cpumask_map will only restrict >>>> to the particular node's cpus which would have really non deterministic >>>> behavior depending on where the code is executed. So in fact we really >>>> want to return cpu_online_mask for NUMA_NO_NODE. >>>> >>>> Some arches were already NUMA_NO_NODE aware, but they return cpu_all_mask, >>>> which should be identical with cpu_online_mask when those arches do not >>>> support cpu hotplug, this patch also changes them to return cpu_online_mask >>>> in order to be consistent and use NUMA_NO_NODE instead of "-1". >>> >>> Except some of those arches *do* support CPU hotplug, powerpc and sparc >>> at least. So switching from cpu_all_mask to cpu_online_mask is a >>> meaningful change. >> >> Yes, thanks for pointing out. >> >>> >>> That doesn't mean it's wrong, but you need to explain why it's the right >>> change. >> >> How about adding the below to the commit log: >> Even if some of the arches do support CPU hotplug, it does not make sense >> to return the cpu that has been hotplugged. >> >> Any suggestion? > > Again, for the third time, I believe. Make it a separate patch please. > There is absolutely no reason to conflate those two things. Ok, thanks. Will make the cpu_all_mask -> cpu_online_mask change a separate patch. Also, do you think it is better to resend this as individual patches for each arch or have all these changes in a single patch? I am not sure which is the common practice for a multi-arches changes like this. >