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=-5.3 required=3.0 tests=BAYES_00, 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 317B5C56202 for ; Thu, 26 Nov 2020 11:05:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C962C2173E for ; Thu, 26 Nov 2020 11:05:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388204AbgKZLFc (ORCPT ); Thu, 26 Nov 2020 06:05:32 -0500 Received: from mx2.suse.de ([195.135.220.15]:39538 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728495AbgKZLFb (ORCPT ); Thu, 26 Nov 2020 06:05:31 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 1DC73AC23; Thu, 26 Nov 2020 11:05:30 +0000 (UTC) Subject: Re: [PATCH next] mm/swap.c: reduce lock contention in lru_cache_add To: Alex Shi Cc: Konstantin Khlebnikov , Andrew Morton , Hugh Dickins , Yu Zhao , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1605860847-47445-1-git-send-email-alex.shi@linux.alibaba.com> From: Vlastimil Babka Message-ID: Date: Thu, 26 Nov 2020 12:05:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/26/20 4:12 AM, Alex Shi wrote: > > > 在 2020/11/25 下午11:38, Vlastimil Babka 写道: >> On 11/20/20 9:27 AM, Alex Shi wrote: >>> The current relock logical will change lru_lock when found a new >>> lruvec, so if 2 memcgs are reading file or alloc page at same time, >>> they could hold the lru_lock alternately, and wait for each other for >>> fairness attribute of ticket spin lock. >>> >>> This patch will sort that all lru_locks and only hold them once in >>> above scenario. That could reduce fairness waiting for lock reget. >>> Than, vm-scalability/case-lru-file-readtwice could get ~5% performance >>> gain on my 2P*20core*HT machine. >> >> Hm, once you sort the pages like this, it's a shame not to splice them instead of more list_del() + list_add() iterations. update_lru_size() could be also called once? > > Yes, looks it's a good idea to use splice instead of list_del/add, but pages > may on different lru list in a same lruvec, and also may come from different > zones. That could involve 5 cycles for different lists, and more for zones... Hmm, zones wouldn't affect splicing (there's a per-node lru these days), but would affect accounting. And yeah, there are 5 lru lists, and we probably need to be under lru lock to stabilize where a page belongs, so pre-sorting without lock wouldn't be safe? Bummer. > I give up the try. >