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=-6.3 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 D7BA9C432BE for ; Thu, 2 Sep 2021 02:23:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AEA2C610C8 for ; Thu, 2 Sep 2021 02:23:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236291AbhIBCYj (ORCPT ); Wed, 1 Sep 2021 22:24:39 -0400 Received: from mga02.intel.com ([134.134.136.20]:24025 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243704AbhIBCYY (ORCPT ); Wed, 1 Sep 2021 22:24:24 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10094"; a="206153851" X-IronPort-AV: E=Sophos;i="5.84,371,1620716400"; d="scan'208";a="206153851" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Sep 2021 19:23:26 -0700 X-IronPort-AV: E=Sophos;i="5.84,371,1620716400"; d="scan'208";a="691080809" Received: from akleen-mobl1.amr.corp.intel.com (HELO [10.209.11.199]) ([10.209.11.199]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Sep 2021 19:23:25 -0700 Subject: Re: [mm] 2d146aa3aa: vm-scalability.throughput -36.4% regression To: Feng Tang Cc: Michal Koutn?? , Johannes Weiner , Linus Torvalds , andi.kleen@intel.com, kernel test robot , Roman Gushchin , Michal Hocko , Shakeel Butt , Balbir Singh , Tejun Heo , Andrew Morton , LKML , lkp@lists.01.org, kernel test robot , "Huang, Ying" , Zhengjun Xing References: <20210816032855.GB72770@shbuild999.sh.intel.com> <20210817024500.GC72770@shbuild999.sh.intel.com> <20210817164737.GA23342@blackbody.suse.cz> <20210818023004.GA17956@shbuild999.sh.intel.com> <20210831063036.GA46357@shbuild999.sh.intel.com> <20210831092304.GA17119@blackbody.suse.cz> <20210901045032.GA21937@shbuild999.sh.intel.com> <877dg0wcrr.fsf@linux.intel.com> <20210902013558.GA97410@shbuild999.sh.intel.com> From: Andi Kleen Message-ID: Date: Wed, 1 Sep 2021 19:23:24 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210902013558.GA97410@shbuild999.sh.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/1/2021 6:35 PM, Feng Tang wrote: > On Wed, Sep 01, 2021 at 08:12:24AM -0700, Andi Kleen wrote: >> Feng Tang writes: >>> Yes, the tests I did is no matter where the 128B padding is added, the >>> performance can be restored and even improved. >> I wonder if we can find some cold, rarely accessed, data to put into the >> padding to not waste it. Perhaps some name strings? Or the destroy >> support, which doesn't sound like its commonly used. > Yes, I tried to move 'destroy_work', 'destroy_rwork' and 'parent' over > before the 'refcnt' together with some padding, it restored the performance > to about 10~15% regression. (debug patch pasted below) > > But I'm not sure if we should use it, before we can fully explain the > regression. Narrowing it down to a single prefetcher seems good enough to me. The behavior of the prefetchers is fairly complicated and hard to predict, so I doubt you'll ever get a 100% step by step explanation. -Andi