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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 B9692C433EF for ; Fri, 24 Sep 2021 09:34:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 990CC61076 for ; Fri, 24 Sep 2021 09:34:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245192AbhIXJgB (ORCPT ); Fri, 24 Sep 2021 05:36:01 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:41628 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237056AbhIXJf7 (ORCPT ); Fri, 24 Sep 2021 05:35:59 -0400 Received: from relay1.suse.de (relay1.suse.de [149.44.160.133]) by smtp-out2.suse.de (Postfix) with ESMTP id F2AAF1FFE0; Fri, 24 Sep 2021 09:34:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1632476066; 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=rDntLQNLN6lkb4wP0qiiEY2Cp52Cp3JUhnteHpFO/Oo=; b=hNW9wJaJWv3vsI422axK/4ZwmDP3wpH8/RQnB9Yq6SGYmh8OUSzBAbB5534mN0ZXJv3PRQ /cQflQkkGM4y1nnJkC01BciIs/ASV5wqN2Y4u1Y6HXnQ5CpCKjEiF5yD5gNoX++lxniizk byWh4W+84H0up/qePINIqRBtPHfXhqA= 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 relay1.suse.de (Postfix) with ESMTPS id DC11E25D3E; Fri, 24 Sep 2021 09:34:25 +0000 (UTC) Date: Fri, 24 Sep 2021 11:34:25 +0200 From: Michal Hocko To: brookxu Cc: hannes@cmpxchg.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: Re: [PATCH 1/2] mem_cgroup: optimize the atomic count of wb_completion Message-ID: References: <1632465983-30525-1-git-send-email-brookxu.cn@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1632465983-30525-1-git-send-email-brookxu.cn@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? -- Michal Hocko SUSE Labs