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=-16.7 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 9ABB4C43460 for ; Tue, 13 Apr 2021 06:58:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 70904613B1 for ; Tue, 13 Apr 2021 06:58:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245276AbhDMG7F (ORCPT ); Tue, 13 Apr 2021 02:59:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44422 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237449AbhDMG6a (ORCPT ); Tue, 13 Apr 2021 02:58:30 -0400 Received: from mail-pg1-x530.google.com (mail-pg1-x530.google.com [IPv6:2607:f8b0:4864:20::530]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 239EEC06134A for ; Mon, 12 Apr 2021 23:57:45 -0700 (PDT) Received: by mail-pg1-x530.google.com with SMTP id p12so11252966pgj.10 for ; Mon, 12 Apr 2021 23:57:45 -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=OtjjYxy6fbQMjrzo3+4P30oz5j5AuPoBCZ8FaKjHWIE=; b=y1rkSqiViCIp3wTOZ5QlJPLXK+Id87VZYWjp1ZyjjVXGVoEX1B6l280oeHYcRpB1KY 9ESkPxUcqthFMWeaWmpwBsPAs3AcKDJrYuUE9hbn1eTCht6iIiiMtfmCcApQBtZCaikL 5dqWFDHSIebonXesBLGxJVCC/6inWWBnQ4RI/iagNc9h3ODaXBWPgo9+IvWilMCTYrpe iQNvJUteDMc1T/AO22JtRuTo36GFapFcy5LB2fzqZTqtpysOxnQsFFqjKSt5VJlECY+I 1pI6Cizi6IduIfyUxUUxlQRg9UqWAuAupLaQsD8V9H8d8Ra3B1qX4jDQpnVQsFnvvMnT yZqA== 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=OtjjYxy6fbQMjrzo3+4P30oz5j5AuPoBCZ8FaKjHWIE=; b=DRFC6QZdMopmBPFv8HJ+L5pNxlxFD0OXvRIeu4GJhgy5ZyzK62O9BN2ekUMForH99n s9cbdkSlp84D/x4HJrFSqEsK4i1J3q8FryWqmoACA2ieb7GYXsPjEPE5lcIeBJdN888k Gfwe/lyA7T1yDXE7Jfd1s9q/tahtmRqcioNLHI86juAgWIaRSOhKinW4/7WsQOBTOjlT Er3qnwpgHQ87uk8OPeaCQIImlPF3vHGiCGWY1IPOt60xo6mJJTd+XfI0SLuWDmvCtOtu Fh6ZkrKFcR7B9Qf0iCuwrXHv4E5I0gX8BWyk1R4y9kvJ3oVqa8z1pUyUIKydcdq2r4dX Zzrw== X-Gm-Message-State: AOAM5305wR5i/9UY/YuedCX5y5Kap2zM8Hpl+VRgbR8wId0fCHUTxBju 3blE7OSYt/aUf8DZIEE7hvwn9A== X-Google-Smtp-Source: ABdhPJy7qTBayD0MjKH9mpcq9ysXSWq3mVkOTjl13qDTm/tP1B8q6Px9uYLgupMSHVay7ks/UL7ooQ== X-Received: by 2002:a62:7b0e:0:b029:24c:3d81:8028 with SMTP id w14-20020a627b0e0000b029024c3d818028mr9200627pfc.58.1618297064697; Mon, 12 Apr 2021 23:57:44 -0700 (PDT) Received: from localhost.localdomain ([139.177.225.241]) by smtp.gmail.com with ESMTPSA id 78sm11508562pfu.40.2021.04.12.23.57.39 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 12 Apr 2021 23:57:44 -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, Muchun Song Subject: [PATCH 2/7] mm: memcontrol: bail out early when !mm in get_mem_cgroup_from_mm Date: Tue, 13 Apr 2021 14:51:48 +0800 Message-Id: <20210413065153.63431-3-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) In-Reply-To: <20210413065153.63431-1-songmuchun@bytedance.com> References: <20210413065153.63431-1-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 Reviewed-by: Shakeel Butt --- 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