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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 9ACADC4742C for ; Mon, 16 Nov 2020 10:04:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 50CFA208C7 for ; Mon, 16 Nov 2020 10:04:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728161AbgKPJb1 (ORCPT ); Mon, 16 Nov 2020 04:31:27 -0500 Received: from mx2.suse.de ([195.135.220.15]:56594 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726156AbgKPJb1 (ORCPT ); Mon, 16 Nov 2020 04:31:27 -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 D6722B03F; Mon, 16 Nov 2020 09:31:25 +0000 (UTC) Message-ID: <1605519085.19452.74.camel@suse.cz> Subject: Re: [x86, sched] 2a0abc5969: phoronix-test-suite.stress-ng.SystemVMessagePassing.bogo_ops_s -14.1% regression From: Giovanni Gherdovich To: kernel test robot Cc: Ingo Molnar , Peter Zijlstra , "Rafael J. Wysocki" , LKML , lkp@lists.01.org, lkp@intel.com, ying.huang@intel.com, feng.tang@intel.com, zhengjun.xing@intel.com, guobing.chen@intel.com, ming.a.chen@intel.com, frank.du@intel.com, Shuhua.Fan@intel.com, wangyang.guo@intel.com, Wenhuan.Huang@intel.com, jessica.ji@intel.com, shan.kang@intel.com, guangli.li@intel.com, tiejun.li@intel.com, yu.ma@intel.com, dapeng1.mi@intel.com, jiebin.sun@intel.com, gengxin.xie@intel.com, fan.zhao@intel.com, aubrey.li@linux.intel.com, yu.c.chen@intel.com Date: Mon, 16 Nov 2020 10:31:25 +0100 In-Reply-To: <20201116070733.GA22371@xsang-OptiPlex-9020> References: <20201116070733.GA22371@xsang-OptiPlex-9020> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2020-11-16 at 15:07 +0800, kernel test robot wrote: > Greeting, > > FYI, we noticed a -14.1% regression of phoronix-test-suite.stress-ng.SystemVMessagePassing.bogo_ops_s due to commit: > > > commit: 2a0abc59699896f03bf6f16efb8a3a490511216f ("x86, sched: Add support for frequency invariance on SKYLAKE_X") > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master > > > in testcase: phoronix-test-suite > on test machine: 96 threads Intel(R) Xeon(R) Gold 6252 CPU @ 2.10GHz with 192G memory > with following parameters: > > test: stress-ng-1.2.2 > option_a: System V Message Passing > cpufreq_governor: performance > ucode: 0x5002f01 I haven't checked this regression yet, but when a "schedutil" change like this patch triggers a regression when the "performance" governor is used, the trouble might come in some roundabout way, eg. from cache alignment issues. The patch defines a number of (not necessarily aligned) per-cpu variables, and there was a recent thread where Boris Petkov, Tony Luck and Mel Gorman debugged something that had similar characteristics: "RE: [LKP] Re: [x86/mce] 1de08dccd3: will-it-scale.per_process_ops -14.1% regression" https://lore.kernel.org/lkml/6e996ad05e434a6fb13f069ee72b876b@intel.com/ I'll study this problem with that in mind. Giovanni