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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 3BBA3C433B4 for ; Fri, 9 Apr 2021 12:32:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F2D961182 for ; Fri, 9 Apr 2021 12:32:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233536AbhDIMcW (ORCPT ); Fri, 9 Apr 2021 08:32:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59056 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231370AbhDIMcV (ORCPT ); Fri, 9 Apr 2021 08:32:21 -0400 Received: from mail-pj1-x1032.google.com (mail-pj1-x1032.google.com [IPv6:2607:f8b0:4864:20::1032]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4333EC061761 for ; Fri, 9 Apr 2021 05:32:04 -0700 (PDT) Received: by mail-pj1-x1032.google.com with SMTP id kk2-20020a17090b4a02b02900c777aa746fso3113710pjb.3 for ; Fri, 09 Apr 2021 05:32:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=i4a9s9eaaqji3vjC/5YOcby1VxJlho+mBaQ9dB0G314=; b=hxZly7/E5IKIeIk6u/EZCEyIoZ/xMYLvSN8rF8942v1a/+cwKmYifDXgBLVJKTj1Yz bpm5VsIWOcAU6I3tPtaofuBvT1HgIAsy26FDVfyheNOij9bcP4XLantQoaBp1IFNolOS zC92u44wbSgqqNgc3ljNUsqbqJVBA1NlDiwUZeaouYqD/Aoj4a24QBBz5o0/6o4MSXu/ 8ojwfYriBdUqDqEq3TbLXQQ3yIQnPoPXD/YYXaycOoMmVNgvC9hfAHsKB6aNYHo00rGo F2urOomjz+EwEnaZJgiTJLdM1ptrfPAqKst4fUI4fyx2KV+gnkUpaRaEzG0UtiHKGzWG 3qsA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=i4a9s9eaaqji3vjC/5YOcby1VxJlho+mBaQ9dB0G314=; b=D360RaWOeTm/2y226Nq/V6Ws+LnpmTPZAmyEvHZtAave50dtDtnNYS/NImcyaiEGSQ uIyxRzJNzbh82PjC6TpoFYxSUW/m4dCee3UdNQy6H/V6zxn7WuLN2LbDTNOzd2PBH69l IzvAbg/mDmbadRxjEwq3OCAk+GcrOu7EPh/PU5gWjaN46auWBCWyV5oE5R0WCZ5CLlf5 wGNCGUg2lHxO4pT8gkOjklSNEEDzAzKLMl2TWB0ridDL2+tx7C0wVBd5937f9RWd9SXk ibuyjP0BZW5c0I94R3GrSDSyHPpaN2x5UCMRQxwthJ7wwSpfmE4kdTQKtnG3xD1vstV7 Fi4A== X-Gm-Message-State: AOAM532YQWcN+OuId0x2zwKOUDh7Wiqn9n3n62J8Ca1t/msC9Y3c7j9g S5GtypgLjHCNvXOrilPkaOV0KA== X-Google-Smtp-Source: ABdhPJxUTMey7XOyvG1I+G4Ben3Ww5Kwa5QoiZhplW2u/vumLA6YeXi0uVU8sX4JsFQHGC5wctmeOw== X-Received: by 2002:a17:90a:4498:: with SMTP id t24mr13735310pjg.78.1617971523836; Fri, 09 Apr 2021 05:32:03 -0700 (PDT) Received: from localhost.localdomain ([139.177.225.243]) by smtp.gmail.com with ESMTPSA id t3sm2167785pfg.176.2021.04.09.05.31.58 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 09 Apr 2021 05:32:03 -0700 (PDT) From: Muchun Song To: guro@fb.com, hannes@cmpxchg.org, mhocko@kernel.org, akpm@linux-foundation.org, shakeelb@google.com, vdavydov.dev@gmail.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, fam.zheng@bytedance.com, bsingharora@gmail.com, shy828301@gmail.com, alex.shi@linux.alibaba.com, Muchun Song Subject: [RFC PATCH v2 02/18] mm: memcontrol: bail out early when !mm in get_mem_cgroup_from_mm Date: Fri, 9 Apr 2021 20:29:43 +0800 Message-Id: <20210409122959.82264-3-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) In-Reply-To: <20210409122959.82264-1-songmuchun@bytedance.com> References: <20210409122959.82264-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When mm is NULL, we do not need to hold rcu lock and call css_tryget for the root memcg. And we also do not need to check !mm in every loop of while. So bail out early when !mm. Signed-off-by: Muchun Song Acked-by: Johannes Weiner --- mm/memcontrol.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f229de925aa5..9cbfff59b171 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -901,20 +901,19 @@ struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm) if (mem_cgroup_disabled()) return NULL; + /* + * Page cache insertions can happen without an + * actual mm context, e.g. during disk probing + * on boot, loopback IO, acct() writes etc. + */ + if (unlikely(!mm)) + return root_mem_cgroup; + rcu_read_lock(); do { - /* - * Page cache insertions can happen without an - * actual mm context, e.g. during disk probing - * on boot, loopback IO, acct() writes etc. - */ - if (unlikely(!mm)) + memcg = mem_cgroup_from_task(rcu_dereference(mm->owner)); + if (unlikely(!memcg)) memcg = root_mem_cgroup; - else { - memcg = mem_cgroup_from_task(rcu_dereference(mm->owner)); - if (unlikely(!memcg)) - memcg = root_mem_cgroup; - } } while (!css_tryget(&memcg->css)); rcu_read_unlock(); return memcg; -- 2.11.0