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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,UNPARSEABLE_RELAY,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 D25BCC433DF for ; Mon, 20 Jul 2020 05:47:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A88E720734 for ; Mon, 20 Jul 2020 05:47:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726618AbgGTFrS (ORCPT ); Mon, 20 Jul 2020 01:47:18 -0400 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:44673 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725872AbgGTFrS (ORCPT ); Mon, 20 Jul 2020 01:47:18 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R181e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01358;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=21;SR=0;TI=SMTPD_---0U3BbMp-_1595224030; Received: from IT-FVFX43SYHV2H.local(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0U3BbMp-_1595224030) by smtp.aliyun-inc.com(127.0.0.1); Mon, 20 Jul 2020 13:47:10 +0800 Subject: Re: [PATCH v16 18/22] mm/lru: replace pgdat lru_lock with lruvec lock To: Alexander Duyck Cc: Andrew Morton , Mel Gorman , Tejun Heo , Hugh Dickins , Konstantin Khlebnikov , Daniel Jordan , Yang Shi , Matthew Wilcox , Johannes Weiner , kbuild test robot , linux-mm , LKML , cgroups@vger.kernel.org, Shakeel Butt , Joonsoo Kim , Wei Yang , "Kirill A. Shutemov" , Michal Hocko , Vladimir Davydov , Rong Chen References: <1594429136-20002-1-git-send-email-alex.shi@linux.alibaba.com> <1594429136-20002-19-git-send-email-alex.shi@linux.alibaba.com> <62dfd262-a7ac-d18e-216a-2988c690b256@linux.alibaba.com> From: Alex Shi Message-ID: <27eb389d-b5f9-fe03-2e57-15c351629efc@linux.alibaba.com> Date: Mon, 20 Jul 2020 13:47:09 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2020/7/19 下午11:14, Alexander Duyck 写道: >> Compare to move to tail, how about to move it to head of struct, which is >> close to lru list? Did you have some data of the place change? > I don't have specific data, just anecdotal evidence from the past that > usually you want to keep locks away from read-mostly items since they > cause obvious cache thrash. My concern was more with the other fields > in the structure such as pgdat since it should be a static value and > having it evicted would likely be more expensive than just leaving the > cacheline as it is. > Thanks for comments, Alex. So, sounds like moving the lru_lock to head of struct lruvec could be better. >> - __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked); >> + if (delta_munlocked) >> + __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked); >> if (lruvec) >> unlock_page_lruvec_irq(lruvec); > Why not just wrap the entire thing in a check for "lruvec"? Yes you > could theoretically be modding with a value of 0, but it avoids a > secondary unnecessary check and branching. Right, and the delta_munlocked value could be checked inside the accounting func Thanks!