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=-10.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 01D08C433E0 for ; Fri, 7 Aug 2020 07:17:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BFB7122CAE for ; Fri, 7 Aug 2020 07:17:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726806AbgHGHR0 (ORCPT ); Fri, 7 Aug 2020 03:17:26 -0400 Received: from mga05.intel.com ([192.55.52.43]:18216 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726038AbgHGHRZ (ORCPT ); Fri, 7 Aug 2020 03:17:25 -0400 IronPort-SDR: niAEalFBLdxcA0n6bWAWRGSlTyRCVVM+xsZX5yPp00mtpSa7D+u6SdMx9Wezu+fJwYENOITMy5 0aWZUo/sSINw== X-IronPort-AV: E=McAfee;i="6000,8403,9705"; a="237871146" X-IronPort-AV: E=Sophos;i="5.75,444,1589266800"; d="scan'208";a="237871146" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Aug 2020 00:17:24 -0700 IronPort-SDR: TW2/Rs+oqVNyglT8SzPM1QCZ+r337k9xEfMIf6xTm3CR693d7jRwYZJWOfJqpBWRiswXg1Gb0R FKA72pWheM4Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,444,1589266800"; d="scan'208";a="289534895" Received: from shao2-debian.sh.intel.com (HELO localhost) ([10.239.13.3]) by orsmga003.jf.intel.com with ESMTP; 07 Aug 2020 00:17:20 -0700 Date: Fri, 7 Aug 2020 15:16:43 +0800 From: kernel test robot To: Ingo Molnar Cc: Dan Williams , Thomas Gleixner , Ingo Molnar , Vishal L Verma , X86 ML , stable , Borislav Petkov , Vivek Goyal , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Linus Torvalds , Tony Luck , Erwin Tsaur , linux-nvdimm , Linux Kernel Mailing List , 0day robot , lkp@lists.01.org Subject: Re: [x86/copy_mc] a0ac629ebe: fio.read_iops -43.3% regression Message-ID: <20200807071643.GL23458@shao2-debian> References: <159630256804.3143511.8894023468833792004.stgit@dwillia2-desk3.amr.corp.intel.com> <20200803094257.GA23458@shao2-debian> <20200806133452.GA2077191@gmail.com> <20200806153500.GC2131635@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200806153500.GC2131635@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, Aug 06, 2020 at 05:35:00PM +0200, Ingo Molnar wrote: > > * Dan Williams wrote: > > > On Thu, Aug 6, 2020 at 6:35 AM Ingo Molnar wrote: > > > > > > > > > * kernel test robot wrote: > > > > > > > Greeting, > > > > > > > > FYI, we noticed a -43.3% regression of fio.read_iops due to commit: > > > > > > > > > > > > commit: a0ac629ebe7b3d248cb93807782a00d9142fdb98 ("x86/copy_mc: Introduce copy_mc_generic()") > > > > url: https://github.com/0day-ci/linux/commits/Dan-Williams/Renovate-memcpy_mcsafe-with-copy_mc_to_-user-kernel/20200802-014046 > > > > > > > > > > > > in testcase: fio-basic > > > > on test machine: 96 threads Intel(R) Xeon(R) Gold 6252 CPU @ 2.10GHz with 256G memory > > > > with following parameters: > > > > > > So this performance regression, if it isn't a spurious result, looks > > > concerning. Is this expected? > > > > This is not expected and I think delays these patches until I'm back > > from leave in a few weeks. I know that we might lose some inlining > > effect due to replacing native memcpy, but I did not expect it would > > have an impact like this. In my testing I was seeing a performance > > improvement from replacing the careful / open-coded copy with rep; > > mov;, which increases the surprise of this result. > > It would be nice to double check this on the kernel-test-robot side as > well, to make sure it's not a false positive. > Hi Ingo, We recompiled the kernels with option "-falign-functions=32", and the regression still exists: 7476b91d4db369d8 a0ac629ebe7b3d248cb9380778 testcase/testparams/testbox ---------------- -------------------------- --------------------------- %stddev change %stddev \ | \ 22103 -43% 12551 fio-basic/2M-performance-2pmem-xfs-libaio-dax-50%-200s-read-200G-tb-ucode=0x5002f01/lkp-csl-2sp6 22103 -43% 12551 GEO-MEAN fio.read_iops Best Regards, Rong Chen