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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 7195FC4338F for ; Tue, 3 Aug 2021 07:11:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 23B6760F58 for ; Tue, 3 Aug 2021 07:11:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 23B6760F58 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id B2F106B0033; 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Tue, 3 Aug 2021 07:11:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1627974687; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=yTB1aRzTEEw2dTSaIA3iMc8Rd5LQIIGML6amfYHIZt4=; b=bwvEpu8IwlMFzHs+yKzQ5BkflANLVPluliOGC2khS0BvVK9MnKiTUjZtExbHtFh63auwUB A2SyUrkYvGA5kzCzUMoQ2b6UCYU84Nn/R6P49iaFug5gcjrDZ5SLblSEEmEXSS6LWs/dko mnKrOFfiafycrcdUJ2jxarlFUwEfmJk= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 114E2A3BCB; Tue, 3 Aug 2021 07:11:26 +0000 (UTC) Date: Tue, 3 Aug 2021 09:11:25 +0200 From: Michal Hocko To: Miaohe Lin Cc: Roman Gushchin , hannes@cmpxchg.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, shakeelb@google.com, willy@infradead.org, alexs@kernel.org, richard.weiyang@gmail.com, songmuchun@bytedance.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: Re: [PATCH 2/5] mm, memcg: narrow the scope of percpu_charge_mutex Message-ID: References: <20210729125755.16871-1-linmiaohe@huawei.com> <20210729125755.16871-3-linmiaohe@huawei.com> <4a3c23c4-054c-2896-29c5-8cf9a4deee98@huawei.com> <95629d91-6ae8-b445-e7fc-b51c888cad59@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <95629d91-6ae8-b445-e7fc-b51c888cad59@huawei.com> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: A7D0E9013A4D Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=bwvEpu8I; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf29.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=mhocko@suse.com X-Stat-Signature: gcpyr946hgokokcyionnebfaj1ngwtes X-HE-Tag: 1627974688-598283 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 Tue 03-08-21 14:29:13, Miaohe Lin wrote: [...] > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 616d1a72ece3..6210b1124929 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2208,11 +2208,11 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) > */ > static void drain_all_stock(struct mem_cgroup *root_memcg) > { > - static DEFINE_MUTEX(percpu_charge_mutex); > int cpu, curcpu; > + static atomic_t drainer = ATOMIC_INIT(0); > > /* If someone's already draining, avoid adding running more workers. */ > - if (!mutex_trylock(&percpu_charge_mutex)) > + if (atomic_cmpxchg(&drainer, 0, 1) != 0) > return; > /* > * Notify other cpus that system-wide "drain" is running > @@ -2244,7 +2244,7 @@ static void drain_all_stock(struct mem_cgroup *root_memcg) > } > } > put_cpu(); > - mutex_unlock(&percpu_charge_mutex); > + atomic_set(&drainer, 0); atomic_set doesn't imply memory barrier IIRC. Is this safe? -- Michal Hocko SUSE Labs