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=-6.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 1B075C55185 for ; Wed, 22 Apr 2020 12:59:17 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CF96B206EC for ; Wed, 22 Apr 2020 12:59:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bCc8yKq7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CF96B206EC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5E52F8E001C; Wed, 22 Apr 2020 08:59:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 597358E0003; Wed, 22 Apr 2020 08:59:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 485468E001C; Wed, 22 Apr 2020 08:59:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0173.hostedemail.com [216.40.44.173]) by kanga.kvack.org (Postfix) with ESMTP id 2DDE98E0003 for ; Wed, 22 Apr 2020 08:59:16 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id E24138248047 for ; Wed, 22 Apr 2020 12:59:15 +0000 (UTC) X-FDA: 76735496670.01.hose93_33bbb98ad4715 X-HE-Tag: hose93_33bbb98ad4715 X-Filterd-Recvd-Size: 7706 Received: from mail-il1-f194.google.com (mail-il1-f194.google.com [209.85.166.194]) by imf47.hostedemail.com (Postfix) with ESMTP for ; Wed, 22 Apr 2020 12:59:15 +0000 (UTC) Received: by mail-il1-f194.google.com with SMTP id f82so1738662ilh.8 for ; Wed, 22 Apr 2020 05:59:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=p3VU98EYy6athLa83fzl0JSs7srbl/nvLU/YB6D/GXA=; b=bCc8yKq7s9jlu57PwRXkaP+ezYZKUq0dMWAElRgLLrURz8NKXC3trFy3gaKZVXOC1z VBcrCmVNUSZlQeBczUPwPZjdWoNZgbA2SjdvK6npCJWQF2Bu82kapMxrPHgeBlf2k7SQ QhmqVZHzLF0g4NzlPuBWJprE2b3bLeFLD3FmUI6Lr+XfMoHjXic1vZ9MMRw0uKzwkBq/ 9DzGX8MTgju/q3nNU19r0fWhCZMh85XbGMHbHl7VgO1R+sWxSz/UMPu5B/oFIx+KLZWM ye8Vd5t1pqDhl1tWBtosh3iIZz+5oQT1VA4fybg51gTBv4124z6BMPc0UhDW7G2doX4f v8kQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=p3VU98EYy6athLa83fzl0JSs7srbl/nvLU/YB6D/GXA=; b=Oe8UzJLMDz5MqWzO5tKAbv4QgUss+0zEkoOy5NZqND9weA1Uf2/3dgLAX+n6v24ipZ HYzr0VvdlOOOb/e53AWcT/Xfgu9OQ2xZ612QG0ZcHNKkfcOa6lcp3mt4dSPlNdsfcqpK 1x9DwKq9eJ6bL4uV99X4RvJ3gdXHFJ6L2QDTYEBYAqq5oGJesUxBbmP7vIuJpMiq+cvR UR20V+Fe7TIwR3PZQOx0ChM2IK4LX4DdY9Bx6M79d1/V9ihFhtH2LuQ2l2gfrDLkPnqz 4pEleD/fvxD0vBkVpo66f5Etkkuopzz58UMnFyllT7RolST5Lrb7OEF3ppI/u/X8pcMy ggig== X-Gm-Message-State: AGi0Pub1+JJRLzQhmSuCobJgTAaMd++zsEccSan+spishyshTnZvvvmh nJnb29OI8NsJx2igPNDpiWeFcrqSq8Aq+zKURcQ= X-Google-Smtp-Source: APiQypJD9qbH3EvzvLldMLBN2Z7fczHbLafY7eFMY9NACkmXKuwPNT+0e8WLclVlyspSWoLPFvjDtFsfFauUtw0rSLg= X-Received: by 2002:a92:c004:: with SMTP id q4mr24822230ild.93.1587560354726; Wed, 22 Apr 2020 05:59:14 -0700 (PDT) MIME-Version: 1.0 References: <20200422110643.15725-1-laoar.shao@gmail.com> <20200422125426.GC358439@cmpxchg.org> In-Reply-To: <20200422125426.GC358439@cmpxchg.org> From: Yafang Shao Date: Wed, 22 Apr 2020 20:58:37 +0800 Message-ID: Subject: Re: [PATCH v2] mm, memcg: fix inconsistent oom event behavior To: Johannes Weiner Cc: Andrew Morton , Michal Hocko , Linux MM , Chris Down , Shakeel Butt Content-Type: text/plain; charset="UTF-8" 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 Wed, Apr 22, 2020 at 8:54 PM Johannes Weiner wrote: > > On Wed, Apr 22, 2020 at 07:06:43AM -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. > > > > Setting CGRP_ROOT_MEMORY_LOCAL_EVENTS for legacy hierarchy by > > default rather than special casing it somewhere quite deep in the code > > would be better, per discussion with Michal. > > > > Fixes: 9852ae3fe529 ("mm, memcg: consider subtrees in memory.events") > > Cc: Chris Down > > Cc: Shakeel Butt > > Cc: Michal Hocko > > Cc: Johannes Weiner > > Signed-off-by: Yafang Shao > > --- > > mm/memcontrol.c | 14 ++++++++++++-- > > 1 file changed, 12 insertions(+), 2 deletions(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 5beea03dd58a..0f7381bddcee 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -5940,10 +5940,20 @@ static void mem_cgroup_bind(struct cgroup_subsys_state *root_css) > > * guarantees that @root doesn't have any children, so turning it > > * on for the root memcg is enough. > > */ > > - if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > > + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) { > > root_mem_cgroup->use_hierarchy = true; > > - else > > + } else { > > root_mem_cgroup->use_hierarchy = false; > > + /* > > + * Set CGRP_ROOT_MEMORY_LOCAL_EVENTS for legacy hierarchy > > + * by default to avoid inconsistent oom_kill behavior > > + * between root memcg and non-root memcg. > > + * Regarding default hierarchy, as this flag will be set > > + * or cleared later, we don't need to process it in this > > + * function. > > + */ > > + cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS; > > That will cause problems for people trying to remount. From > cgroup1_reconfigure(): > > /* Don't allow flags or name to change at remount */ > if ((ctx->flags ^ root->flags) || > (ctx->name && strcmp(ctx->name, root->name))) { > errorfc(fc, "option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"", > ctx->flags, ctx->name ?: "", root->flags, root->name); > ret = -EINVAL; > goto out_unlock; > } > > These flags belong to the user, they're read-only to the cgroup > implementation. Let's not mess with them from a controller. > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 4b868e5a687f..e831a90b5506 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -773,6 +773,8 @@ 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)) && Hi Johnanes, That is what I did in the previous version, see also https://lore.kernel.org/linux-mm/20200414015952.3590-1-laoar.shao@gmail.com/ . -- Thanks Yafang