From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751280AbdH1NNc (ORCPT ); Mon, 28 Aug 2017 09:13:32 -0400 Received: from mx2.suse.de ([195.135.220.15]:53319 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751170AbdH1NNa (ORCPT ); Mon, 28 Aug 2017 09:13:30 -0400 Date: Mon, 28 Aug 2017 15:13:28 +0200 From: Michal Hocko To: Will Deacon Cc: Zhen Lei , linux-kernel , linux-api , Greg Kroah-Hartman , linux-mm , Zefan Li , Xinwei Hu , Tianhong Ding , Hanjun Guo , Catalin Marinas Subject: Re: [PATCH 1/1] mm: only dispaly online cpus of the numa node Message-ID: <20170828131328.GM17097@dhcp22.suse.cz> References: <1497962608-12756-1-git-send-email-thunder.leizhen@huawei.com> <20170824083225.GA5943@dhcp22.suse.cz> <20170825173433.GB26878@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170825173433.GB26878@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 25-08-17 18:34:33, Will Deacon wrote: > On Thu, Aug 24, 2017 at 10:32:26AM +0200, Michal Hocko wrote: > > It seems this has slipped through cracks. Let's CC arm64 guys > > > > On Tue 20-06-17 20:43:28, Zhen Lei wrote: > > > When I executed numactl -H(which read /sys/devices/system/node/nodeX/cpumap > > > and display cpumask_of_node for each node), but I got different result on > > > X86 and arm64. For each numa node, the former only displayed online CPUs, > > > and the latter displayed all possible CPUs. Unfortunately, both Linux > > > documentation and numactl manual have not described it clear. > > > > > > I sent a mail to ask for help, and Michal Hocko replied > > > that he preferred to print online cpus because it doesn't really make much > > > sense to bind anything on offline nodes. > > > > Yes printing offline CPUs is just confusing and more so when the > > behavior is not consistent over architectures. I believe that x86 > > behavior is the more appropriate one because it is more logical to dump > > the NUMA topology and use it for affinity setting than adding one > > additional step to check the cpu state to achieve the same. > > > > It is true that the online/offline state might change at any time so the > > above might be tricky on its own but if we should at least make the > > behavior consistent. > > > > > Signed-off-by: Zhen Lei > > > > Acked-by: Michal Hocko > > The concept looks find to me, but shouldn't we use cpumask_var_t and > alloc/free_cpumask_var? This will be safer but both callers of node_read_cpumap are shallow stack so I am not sure a stack is a limiting factor here. Zhen Lei, would you care to update that part please? -- Michal Hocko SUSE Labs