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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=unavailable 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 69D42C43603 for ; Thu, 5 Dec 2019 17:05:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 313462464D for ; Thu, 5 Dec 2019 17:05:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 313462464D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BBF476B113C; Thu, 5 Dec 2019 12:05:22 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B6FF16B113D; Thu, 5 Dec 2019 12:05:22 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A86B26B113E; Thu, 5 Dec 2019 12:05:22 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0102.hostedemail.com [216.40.44.102]) by kanga.kvack.org (Postfix) with ESMTP id 8DA286B113C for ; Thu, 5 Dec 2019 12:05:22 -0500 (EST) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 2E11D82E0739 for ; Thu, 5 Dec 2019 17:05:22 +0000 (UTC) X-FDA: 76231713684.01.shake04_4bdbf419f1146 X-HE-Tag: shake04_4bdbf419f1146 X-Filterd-Recvd-Size: 4784 Received: from out30-54.freemail.mail.aliyun.com (out30-54.freemail.mail.aliyun.com [115.124.30.54]) by imf28.hostedemail.com (Postfix) with ESMTP for ; Thu, 5 Dec 2019 17:05:20 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01422;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0Tk3Ek6d_1575565511; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0Tk3Ek6d_1575565511) by smtp.aliyun-inc.com(127.0.0.1); Fri, 06 Dec 2019 01:05:15 +0800 Subject: Re: [PATCH] mm: vmscan: protect shrinker idr replace with CONFIG_MEMCG To: Kirill Tkhai , Michal Hocko Cc: hannes@cmpxchg.org, shakeelb@google.com, guro@fb.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1575486978-45249-1-git-send-email-yang.shi@linux.alibaba.com> <20191205094341.GC28317@dhcp22.suse.cz> <894b9951-449d-6d7e-84aa-a1c510417710@virtuozzo.com> <80918583-da44-71f0-8c94-224a3268577c@virtuozzo.com> From: Yang Shi Message-ID: Date: Thu, 5 Dec 2019 09:05:09 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <80918583-da44-71f0-8c94-224a3268577c@virtuozzo.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US 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 12/5/19 2:11 AM, Kirill Tkhai wrote: > On 05.12.2019 13:00, Kirill Tkhai wrote: >> On 05.12.2019 12:43, Michal Hocko wrote: >>> On Thu 05-12-19 11:23:28, Kirill Tkhai wrote: >>>> On 04.12.2019 22:16, Yang Shi wrote: >>>>> Since commit 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker: >>>>> make shrinker not depend on memcg kmem"), shrinkers' idr is protected by >>>>> CONFIG_MEMCG instead of CONFIG_MEMCG_KMEM, so it makes no sense to >>>>> protect shrinker idr replace with CONFIG_MEMCG_KMEM. >>>>> >>>>> Cc: Kirill Tkhai >>>>> Cc: Johannes Weiner >>>>> Cc: Michal Hocko >>>>> Cc: Shakeel Butt >>>>> Cc: Roman Gushchin >>>>> Signed-off-by: Yang Shi >>>> It looks like that in CONFIG_SLOB case we do not even call some shrinkers >>>> for subordinate mem cgroups (i.e., we don't call deferred_split_shrinker), >>>> since they never become completely registered. >>>> >>>> Fixes: 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 ("mm: shrinker: make shrinker not depend on memcg kmem") >>> I am confused. Why the Fixes tag? Nothing should be really broken with >>> KMEM config guard right? >> idr_replace() is disabled in CONFIG_MEMCG && CONFIG_SLOB case, and this is >> wrong. >> >> 0a432dcbeb32edcd211a5d8f7847d0da7642a8b4 goes in the series, which enables >> shrinker_idr infrastructure for huge_memory.c's deferred_split_shrinker >> in CONFIG_MEMCG case. Previously, all SHRINKER_MEMCG_AWARE shrinkers were >> based on LRUs, and they remain to base of CONFIG_MEMCG_KMEM. >> But deferred_split_shrinker is an exception. >> >> In CONFIG_MEMCG && CONFIG_SLOB case, shrinker_idr contains only shrinker, >> and it is deferred_split_shrinker. But it is never actually called, since >> idr_replace() is never compiled. deferred_split_shrinker all the time is >> staying in half-registered state, and it's never called for subordinate >> mem cgroups. >> >> So, this is a BUG, and this should go to stable. > The visible effect is that deferred_split_shrinker is never called > from shrink_slab() for subordinate mem cgroups. It's called only > for root_mem_cgroup. Thanks for noticing the SLOB case, I didn't realize it and thought it was just a cleanup too. Will update the information and cc to stable list for v2. > >>> This is a mere clean up AFAICS. >>> >>>> Reviewed-by: Kirill Tkhai >>>> >>>>> --- >>>>> mm/vmscan.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>>>> index ee4eecc..e7f10c4 100644 >>>>> --- a/mm/vmscan.c >>>>> +++ b/mm/vmscan.c >>>>> @@ -422,7 +422,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) >>>>> { >>>>> down_write(&shrinker_rwsem); >>>>> list_add_tail(&shrinker->list, &shrinker_list); >>>>> -#ifdef CONFIG_MEMCG_KMEM >>>>> +#ifdef CONFIG_MEMCG >>>>> if (shrinker->flags & SHRINKER_MEMCG_AWARE) >>>>> idr_replace(&shrinker_idr, shrinker, shrinker->id); >>>>> #endif >>>>>