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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 BCC7FC3A5A9 for ; Mon, 4 May 2020 23:03:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 71E412075B for ; Mon, 4 May 2020 23:03:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="UEhbGIyT" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 71E412075B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 206A58E008A; Mon, 4 May 2020 19:03:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1B7A58E0058; Mon, 4 May 2020 19:03:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0F4BA8E008A; Mon, 4 May 2020 19:03:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0045.hostedemail.com [216.40.44.45]) by kanga.kvack.org (Postfix) with ESMTP id EA6CC8E0058 for ; Mon, 4 May 2020 19:03:49 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id AEF01138F0 for ; Mon, 4 May 2020 23:03:49 +0000 (UTC) X-FDA: 76780565778.18.baby21_3e7af62135507 X-HE-Tag: baby21_3e7af62135507 X-Filterd-Recvd-Size: 3740 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Mon, 4 May 2020 23:03:49 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 3DF222075B; Mon, 4 May 2020 23:03:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588633428; bh=JfEwLdWlzm1pij4miQJh5HXzpB9EyH8O2AaDlkeMbA0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=UEhbGIyTWbSHlZIeJ3G/ukyJnvsZ9TY0dJUpj47IAzKKOMRm1mKGWto+53ouTElZn 4NfRzaDceMPej5dcvw7Uxeo2M5rRhPQnWNcrD85izNWo+r3A5BZMICIkSpEUivqi9A MX/UdeQNL9vqML3NZVEULVno/0GoHY8W9Od5Hao0= Date: Mon, 4 May 2020 16:03:45 -0700 From: Andrew Morton To: Yafang Shao Cc: linux-mm@kvack.org, Chris Down , Michal Hocko , Johannes Weiner Subject: Re: [PATCH resend] mm, memcg: fix inconsistent oom event behavior Message-Id: <20200504160345.45801b7bf199ac5897e2572a@linux-foundation.org> In-Reply-To: <20200502141055.7378-1-laoar.shao@gmail.com> References: <20200502141055.7378-1-laoar.shao@gmail.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, 2 May 2020 10:10:55 -0400 Yafang Shao wrote: > A recent commit 9852ae3fe529 ("mm, memcg: consider subtrees in > memory.events") changes the behavior of memcg events, which will > consider subtrees in memory.events. But oom_kill event is a special one > as it is used in both cgroup1 and cgroup2. In cgroup1, it is displayed > in memory.oom_control. The file memory.oom_control is in both root memcg > and non root memcg, that is different with memory.event as it only in > non-root memcg. That commit is okay for cgroup2, but it is not okay for > cgroup1 as it will cause inconsistent behavior between root memcg and > non-root memcg. > > Here's an example on why this behavior is inconsistent in cgroup1. > root memcg > / > memcg foo > / > memcg bar > > Suppose there's an oom_kill in memcg bar, then the oon_kill will be > > root memcg : memory.oom_control(oom_kill) 0 > / > memcg foo : memory.oom_control(oom_kill) 1 > / > memcg bar : memory.oom_control(oom_kill) 1 > > For the non-root memcg, its memory.oom_control(oom_kill) includes its > descendants' oom_kill, but for root memcg, it doesn't include its > descendants' oom_kill. That means, memory.oom_control(oom_kill) has > different meanings in different memcgs. That is inconsistent. Then the user > has to know whether the memcg is root or not. > > If we can't fully support it in cgroup1, for example by adding > memory.events.local into cgroup1 as well, then let's don't touch > its original behavior. > > Fixes: 9852ae3fe529 ("mm, memcg: consider subtrees in memory.events") Nearly a year ago. Should we backport this into earlier kernels? > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -783,6 +783,8 @@ static inline void memcg_memory_event(struct mem_cgroup *memcg, > atomic_long_inc(&memcg->memory_events[event]); > cgroup_file_notify(&memcg->events_file); > > + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) > + break; > if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS) > break; > } while ((memcg = parent_mem_cgroup(memcg)) &&