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, USER_AGENT_SANE_1 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 AE47DCA90AF for ; Wed, 13 May 2020 11:20:06 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6FA2720753 for ; Wed, 13 May 2020 11:20:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6FA2720753 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EA5BA900124; Wed, 13 May 2020 07:20:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E56B19000F3; Wed, 13 May 2020 07:20:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D4512900124; Wed, 13 May 2020 07:20:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0037.hostedemail.com [216.40.44.37]) by kanga.kvack.org (Postfix) with ESMTP id B8F099000F3 for ; Wed, 13 May 2020 07:20:05 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 793D9249C for ; Wed, 13 May 2020 11:20:05 +0000 (UTC) X-FDA: 76811451570.01.thumb10_74f91ed74384f X-HE-Tag: thumb10_74f91ed74384f X-Filterd-Recvd-Size: 2697 Received: from huawei.com (szxga05-in.huawei.com [45.249.212.191]) by imf46.hostedemail.com (Postfix) with ESMTP for ; Wed, 13 May 2020 11:20:03 +0000 (UTC) Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 5866B8E1CE9EE32307A9; Wed, 13 May 2020 19:20:00 +0800 (CST) Received: from [10.133.206.78] (10.133.206.78) by smtp.huawei.com (10.3.19.212) with Microsoft SMTP Server (TLS) id 14.3.487.0; Wed, 13 May 2020 19:19:57 +0800 Subject: Re: [PATCH] memcg: Fix memcg_kmem_bypass() for remote memcg charging To: Michal Hocko CC: Johannes Weiner , Vladimir Davydov , Cgroups , , Andrew Morton References: <20200513090502.GV29153@dhcp22.suse.cz> From: Zefan Li Message-ID: <76f71776-d049-7407-8574-86b6e9d80704@huawei.com> Date: Wed, 13 May 2020 19:19:56 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: <20200513090502.GV29153@dhcp22.suse.cz> Content-Type: text/plain; charset="gbk" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.133.206.78] X-CFilter-Loop: Reflected 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 2020/5/13 17:05, Michal Hocko wrote: > On Wed 13-05-20 15:28:28, Li Zefan wrote: >> While trying to use remote memcg charging in an out-of-tree kernel module >> I found it's not working, because the current thread is a workqueue thread. >> >> Signed-off-by: Zefan Li >> --- >> >> No need to queue this for v5.7 as currently no upstream users of this memcg >> feature suffer from this bug. >> >> --- >> mm/memcontrol.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index a3b97f1..db836fc 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -2802,6 +2802,8 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg, >> >> static inline bool memcg_kmem_bypass(void) >> { >> + if (unlikely(current->active_memcg)) >> + return false; > > I am confused. Why the check below is insufficient? It checks for both mm > and PF_KTHREAD? > memalloc_use_memcg(memcg); alloc_page(GFP_KERNEL_ACCOUNT); memalloc_unuse_memcg(); If we run above code in a workqueue thread the memory won't be charged to the specific memcg, because memcg_kmem_bypass() returns true in this case. >> if (in_interrupt() || !current->mm || (current->flags & PF_KTHREAD)) >> return true; >> return false;