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 2B376C6FA82 for ; Fri, 23 Sep 2022 07:29:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231124AbiIWH3N (ORCPT ); Fri, 23 Sep 2022 03:29:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40748 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229606AbiIWH3H (ORCPT ); Fri, 23 Sep 2022 03:29:07 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 835AF12B5C4; Fri, 23 Sep 2022 00:29:05 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 3CD44218FA; Fri, 23 Sep 2022 07:29:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1663918144; h=from:from:reply-to: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=rOM18LotnWoAueDS7CKAxKNZg+usqMDivdcE9JRJPBE=; b=dVnRMWYNhplQavDtc54h2Ex/j2jYR77RBKGgq9v2Rjc1hmm4joAkkKC8VCpEp/rjz3GJ3D E2XRU17CR4X2WBeCgaI2Yt3Emris/lMgFiGkurmrvA65OOPU02Kjg7PUOixpnvsGhUOrLK X1I7y+0RI28a/Znu5Spp2d+yb3u9Xq0= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 2C79913A00; Fri, 23 Sep 2022 07:29:04 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id JIcMCkBgLWM9bAAAMHmgww (envelope-from ); Fri, 23 Sep 2022 07:29:04 +0000 Date: Fri, 23 Sep 2022 09:29:03 +0200 From: Michal Hocko To: Zhongkun He Cc: hannes@cmpxchg.org, roman.gushchin@linux.dev, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, lizefan.x@bytedance.com, wuyun.abel@bytedance.com Subject: Re: [External] Re: [PATCH] cgroup/cpuset: Add a new isolated mems.policy type. Message-ID: References: <20220904040241.1708-1-hezhongkun.hzk@bytedance.com> <0e5f380b-9201-0f56-9144-ce8449491fc8@bytedance.com> <93d76370-6c43-5560-9a5f-f76a8cc979e0@bytedance.com> <120cb50d-d617-a60a-ec24-915f826318f1@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <120cb50d-d617-a60a-ec24-915f826318f1@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 14-09-22 23:10:47, Zhongkun He wrote: > > > > > > > Back to the previous question. > > > > > The question is how to implement that with a sensible semantic. > > > > > > > > Thanks for your analysis and suggestions.It is really difficult to add > > > > policy directly to cgroup for the hierarchical enforcement. It > > > > would be a good idea to add pidfd_set_mempolicy. > > > > > > Are you going to pursue that path? > > > Hi Michal, thanks for your suggestion and reply. > > > > > Are you going to pursue that path? > > > > Yes，I'll give it a try as it makes sense to modify the policy dynamically. > > > > Thanks. > > Hi Michal, i have a question about pidfd_set_mempolicy, it would be better > if you have some suggestions. > > The task_struct of processes and threads are independent. If we change the > mempolicy of the process through pidfd_set_mempolicy, the mempolicy of its > thread will not change. Of course users can set the mempolicy of all threads > by iterating through /proc/tgid/task. > > The question is whether we should override the thread's mempolicy when > setting the process's mempolicy. > > There are two options: > A:Change the process's mempolicy and set that mempolicy to all it's threads. > B:Only change the process's mempolicy in kernel. The mempolicy of the thread > needs to be modified by the user through pidfd_set_mempolicy in > userspace, if necessary. set_mempolicy is a per task_struct operation and so should be pidfd based API as well. If somebody requires a per-thread-group setting then the whole group should be iterated. I do not think we have any precendence where pidfd operation on the thread group leader has side effects on other threads as well. -- Michal Hocko SUSE Labs