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=-4.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 C783BC433EF for ; Fri, 24 Sep 2021 13:26:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE17460F4C for ; Fri, 24 Sep 2021 13:26:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346079AbhIXN2N (ORCPT ); Fri, 24 Sep 2021 09:28:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50912 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344885AbhIXN2C (ORCPT ); Fri, 24 Sep 2021 09:28:02 -0400 Received: from mail-pf1-x429.google.com (mail-pf1-x429.google.com [IPv6:2607:f8b0:4864:20::429]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94F0EC0A888B; Fri, 24 Sep 2021 06:02:55 -0700 (PDT) Received: by mail-pf1-x429.google.com with SMTP id q23so8810095pfs.9; Fri, 24 Sep 2021 06:02:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=0k4GidOpDOZlh4Z8G1WDVmPhA4Roxd0DMwZbEhyIkW0=; b=HmA3vYJrpvO5HCGcY/nOKAYXKJu2tMpAza2IwZBLmiwaBi3bpCiqGsRD2YiJi0Wpqd HQxVniQ+PdUJ/RcQQCVgacoFTkaDXsyLkbZ+huAdUO3/QrK756amHJ17LFNDSGW3M6Hf pr74o52t++xDu6/0SgJAwWwOuFtCGZzhpKHMCdt9rPK2l9t1f1Q0paQk1c6tjmZbW6Qo Fu+3/LqZIprNu82Ub/Appl8ZvLQjaOigNzq+sFA9+BIo4QKiqmEoJCwpIXYe9oX4pCG9 RNPJPnUKD8MtfuCabWGyYSveEl1ShulzpiXzOk9zZcQsNdyftKW76tGLtf2BG1OFoGbO AUgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=0k4GidOpDOZlh4Z8G1WDVmPhA4Roxd0DMwZbEhyIkW0=; b=qnf1o0ReVuGVgAkO1FXZpaF/2zqk5V/9BnIwmScwlQcQz00CrhbLBGg34ikw+/4HIL 0O6Z7BXzQIgochqJKmqbWHqUOcFQmYy1QosnmZIsencEGR9hQYwKVj190Hgp8ThZgPkr I8vwrVOgfckrOINH6tXl0mdDwJ5BTODPTl9Otske8pkHweKnRjTBepSA0jsFWARZDuzA PacGLnsNGafBL0yFTWZS1Fah5NjbKRyYL7lByS66PmBXtiXhJkuF3YJT1yYemx/qophN tyW7u6BrUXFHu/FXVgJ6mMkvGdalBKQMzxBoHgQH69RSr/BRwuOg7HaudyPQZt+q3nx7 puCg== X-Gm-Message-State: AOAM533UAOaCZ+vqbYaagMntP8KF6q62F6w9ePUzFcwW2kSz4p+YaMp0 xdiBsjy1cppqjbW+87K1DQKe3eCjGkeE0g== X-Google-Smtp-Source: ABdhPJz9zpVB4OsMX45ZrXC1ocVLVZ3gIGIp3sQBJS7/mWuhM3iTWdSyzvklHfx99GufppPE7an5nw== X-Received: by 2002:a62:4dc5:0:b0:438:8133:fcef with SMTP id a188-20020a624dc5000000b004388133fcefmr9646405pfb.44.1632488574952; Fri, 24 Sep 2021 06:02:54 -0700 (PDT) Received: from [192.168.255.10] ([203.205.141.113]) by smtp.gmail.com with ESMTPSA id x15sm9955227pgt.34.2021.09.24.06.02.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Sep 2021 06:02:54 -0700 (PDT) Subject: Re: [PATCH 1/2] mem_cgroup: optimize the atomic count of wb_completion To: Michal Hocko Cc: hannes@cmpxchg.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org References: <1632465983-30525-1-git-send-email-brookxu.cn@gmail.com> From: brookxu Message-ID: <03145735-7764-4cd4-e15b-60402f4b447e@gmail.com> Date: Fri, 24 Sep 2021 21:02:52 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks for your time. Michal Hocko wrote on 2021/9/24 17:34: > On Fri 24-09-21 14:46:22, brookxu wrote: >> From: Chunguang Xu >> >> In order to track inflight foreign writeback, we init >> wb_completion.cnt to 1. For normal writeback, this cause >> wb_wait_for_completion() to perform meaningless atomic >> operations. Since foreign writebacks rarely occur in most >> scenarios, we can init wb_completion.cnt to 0 and set >> frn.done.cnt to 1. In this way we can avoid unnecessary >> atomic operations. > > Does this lead to any measurable differences? I created multiple cgroups that performed IO on multiple disks, then flushed the cache with sync command, and no measurable differences have been observed so far. >