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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 5B698C433E0 for ; Mon, 4 Jan 2021 13:04:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E53D921BE5 for ; Mon, 4 Jan 2021 13:04:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E53D921BE5 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 08AB86B0098; Mon, 4 Jan 2021 08:04:01 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 039406B009C; Mon, 4 Jan 2021 08:04:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E91FE6B009E; Mon, 4 Jan 2021 08:04:00 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0009.hostedemail.com [216.40.44.9]) by kanga.kvack.org (Postfix) with ESMTP id D46466B0098 for ; Mon, 4 Jan 2021 08:04:00 -0500 (EST) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 86478362B for ; Mon, 4 Jan 2021 13:04:00 +0000 (UTC) X-FDA: 77668110240.11.net20_5c1041e274d0 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin11.hostedemail.com (Postfix) with ESMTP id 62938180F8B82 for ; Mon, 4 Jan 2021 13:04:00 +0000 (UTC) X-HE-Tag: net20_5c1041e274d0 X-Filterd-Recvd-Size: 4120 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Mon, 4 Jan 2021 13:03:59 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1609765438; 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=vibaRJ3VEeCNwuYRgupkbYHsXd/lrAoVedXx0JmGMyw=; b=AvzCZDX6SWN4RvUPRK1ZySQleecMLM8R6orz8os3JfH99EDKEGYuFkut7otZbLrf+jPlhr M9x7JEihGX91WZZsj4ZAYcdIky2i16bDwj8RxqoxyNCotXu8Cy9Bpwlyb9DtfAcolhRq6n hbe0hsgvtmCjOKCbkJWPilXMg8I/1ZA= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 84C07AD19; Mon, 4 Jan 2021 13:03:58 +0000 (UTC) Date: Mon, 4 Jan 2021 14:03:57 +0100 From: Michal Hocko To: Feng Tang Cc: Andrew Morton , Johannes Weiner , Vladimir Davydov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, andi.kleen@intel.com, tim.c.chen@intel.com, dave.hansen@intel.com, ying.huang@intel.com, Roman Gushchin Subject: Re: [PATCH 1/2] mm: page_counter: relayout structure to reduce false sharing Message-ID: <20210104130357.GF13207@dhcp22.suse.cz> References: <1609252514-27795-1-git-send-email-feng.tang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1609252514-27795-1-git-send-email-feng.tang@intel.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue 29-12-20 22:35:13, Feng Tang wrote: > When checking a memory cgroup related performance regression [1], > from the perf c2c profiling data, we found high false sharing for > accessing 'usage' and 'parent'. > > On 64 bit system, the 'usage' and 'parent' are close to each other, > and easy to be in one cacheline (for cacheline size == 64+ B). 'usage' > is usally written, while 'parent' is usually read as the cgroup's > hierarchical counting nature. > > So move the 'parent' to the end of the structure to make sure they > are in different cache lines. Yes, parent is write-once field so having it away from other heavy RW fields makes sense to me. > Following are some performance data with the patch, against > v5.11-rc1, on several generations of Xeon platforms. Most of the > results are improvements, with only one malloc case on one platform > shows a -4.0% regression. Each category below has several subcases > run on different platform, and only the worst and best scores are > listed: > > fio: +1.8% ~ +8.3% > will-it-scale/malloc1: -4.0% ~ +8.9% > will-it-scale/page_fault1: no change > will-it-scale/page_fault2: +2.4% ~ +20.2% What is the second number? Std? > [1].https://lore.kernel.org/lkml/20201102091543.GM31092@shao2-debian/ > Signed-off-by: Feng Tang > Cc: Roman Gushchin > Cc: Johannes Weiner > --- > include/linux/page_counter.h | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/include/linux/page_counter.h b/include/linux/page_counter.h > index 85bd413..6795913 100644 > --- a/include/linux/page_counter.h > +++ b/include/linux/page_counter.h > @@ -12,7 +12,6 @@ struct page_counter { > unsigned long low; > unsigned long high; > unsigned long max; > - struct page_counter *parent; > > /* effective memory.min and memory.min usage tracking */ > unsigned long emin; > @@ -27,6 +26,14 @@ struct page_counter { > /* legacy */ > unsigned long watermark; > unsigned long failcnt; > + > + /* > + * 'parent' is placed here to be far from 'usage' to reduce > + * cache false sharing, as 'usage' is written mostly while > + * parent is frequently read for cgroup's hierarchical > + * counting nature. > + */ > + struct page_counter *parent; > }; > > #if BITS_PER_LONG == 32 > -- > 2.7.4 > -- Michal Hocko SUSE Labs