From patchwork Tue Dec 29 14:35:13 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Feng Tang X-Patchwork-Id: 11992443 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 24B3EC433DB for ; Tue, 29 Dec 2020 14:35:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9C69E20825 for ; Tue, 29 Dec 2020 14:35:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9C69E20825 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 951B58D002D; Tue, 29 Dec 2020 09:35:23 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 900D88D002C; Tue, 29 Dec 2020 09:35:23 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 819118D002D; Tue, 29 Dec 2020 09:35:23 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 6D03E8D002C for ; Tue, 29 Dec 2020 09:35:23 -0500 (EST) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 212B48249980 for ; Tue, 29 Dec 2020 14:35:23 +0000 (UTC) X-FDA: 77646567726.26.worm99_200ee892749d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id E402F1804B65A for ; Tue, 29 Dec 2020 14:35:22 +0000 (UTC) X-HE-Tag: worm99_200ee892749d X-Filterd-Recvd-Size: 3682 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Tue, 29 Dec 2020 14:35:20 +0000 (UTC) IronPort-SDR: DQTlbItKicezHMvjazzt3hZQbdXUELzBzjuaptGB/6sDR1++t2HntqsWUIO3Uut7DcW7kwZXUt ze5FQISH3GWA== X-IronPort-AV: E=McAfee;i="6000,8403,9849"; a="238051116" X-IronPort-AV: E=Sophos;i="5.78,458,1599548400"; d="scan'208";a="238051116" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Dec 2020 06:35:18 -0800 IronPort-SDR: 90Tie2bCZPBy/9Ux/SljHFQW6M/rurKEfGWOYmOFx7dMBOJtv+/ehiW22sam+UhhnQ1/zeywBI IjAXYLa4RmPQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.78,458,1599548400"; d="scan'208";a="419194790" Received: from shbuild999.sh.intel.com ([10.239.147.98]) by orsmga001.jf.intel.com with ESMTP; 29 Dec 2020 06:35:15 -0800 From: Feng Tang To: Andrew Morton , Michal Hocko , Johannes Weiner , Vladimir Davydov , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, andi.kleen@intel.com, tim.c.chen@intel.com, dave.hansen@intel.com, ying.huang@intel.com, Feng Tang , Roman Gushchin Subject: [PATCH 1/2] mm: page_counter: relayout structure to reduce false sharing Date: Tue, 29 Dec 2020 22:35:13 +0800 Message-Id: <1609252514-27795-1-git-send-email-feng.tang@intel.com> X-Mailer: git-send-email 2.7.4 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: 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. 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% [1].https://lore.kernel.org/lkml/20201102091543.GM31092@shao2-debian/ Signed-off-by: Feng Tang Cc: Roman Gushchin Cc: Johannes Weiner Reviewed-by: Roman Gushchin --- 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