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, NICE_REPLY_A,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 3F42DC56202 for ; Fri, 20 Nov 2020 23:19:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D62902242A for ; Fri, 20 Nov 2020 23:19:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="FM0WixIh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728781AbgKTXTu (ORCPT ); Fri, 20 Nov 2020 18:19:50 -0500 Received: from mail.kernel.org ([198.145.29.99]:46436 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728124AbgKTXTt (ORCPT ); Fri, 20 Nov 2020 18:19:49 -0500 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BFFEF2240C; Fri, 20 Nov 2020 23:19:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1605914389; bh=CgKb22sqL72nT7lPhX4BhOYK565Z8Zz2St8cZ261t+U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=FM0WixIhD8TuccCPJXLzguGZIUhfQlPCO5mOwYN+W01KpSNVZTdxEjjnw0uX5ORus klzQeKNh7Du+eWGTqXM2978qjY/ozbXl0NdWcxL9T6z4vBYBHNDL2G2b7neMd/Uo1C lNXc3gRtQi1QxA0izArBvqCfn93EdvrQjEBbXCig= Date: Fri, 20 Nov 2020 15:19:48 -0800 From: Andrew Morton To: Alex Shi Cc: Konstantin Khlebnikov , Hugh Dickins , Yu Zhao , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH next] mm/swap.c: reduce lock contention in lru_cache_add Message-Id: <20201120151948.c3f4175ed18ed74e46760b87@linux-foundation.org> In-Reply-To: <1605860847-47445-1-git-send-email-alex.shi@linux.alibaba.com> References: <1605860847-47445-1-git-send-email-alex.shi@linux.alibaba.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 20 Nov 2020 16:27:27 +0800 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. But what happens when all or most of the pages belong to the same lruvec? This sounds like the common case - won't it suffer?