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=-9.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, 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 1BEF4C433E0 for ; Thu, 6 Aug 2020 16:51:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5956823119 for ; Thu, 6 Aug 2020 16:51:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596732670; bh=sPqT44CYHNyOG5pq4JVNEebprcgrQJyMEDJGkP9TKms=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=UrYxOdplUXSEbsWXXaljuECCIWU+GkrnyhgWmMqQt1G87ji6o8XdDfLi1iIumkc53 go8dYLPQlScHMsVzP2Bh4ZlK2g6uu+YIAA8S/Lj4Bo2hCra7eq64ljoPOYFJKw5OVh olsLMrtPnB827A9hnE7i/ipBUnYtGiyz1E4JNpfI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729272AbgHFQvD (ORCPT ); Thu, 6 Aug 2020 12:51:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43232 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729555AbgHFQuN (ORCPT ); Thu, 6 Aug 2020 12:50:13 -0400 Received: from mail-ej1-x643.google.com (mail-ej1-x643.google.com [IPv6:2a00:1450:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8E497C0086B8; Thu, 6 Aug 2020 08:35:08 -0700 (PDT) Received: by mail-ej1-x643.google.com with SMTP id m22so7692552eje.10; Thu, 06 Aug 2020 08:35:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=jAnZHwKItrjXdvdR58QzqOoGM6YiK6Tg67ZIO3IEXZQ=; b=PaV9DzcXBRT4XdiWVj2xuDnpNzGzZvTVchEJ29eJg3AwKErvnq9AkPTWImWIdPrvSk Cm1fi9ZxhQcs1r7k5zNMztQZEJqDMdu4nka/5tt8Hhb9cFcUnBoSa31kj9ZW0F5Bwztk NHaIsLTKVw7u8qV/lSP5g3fWoeyPzO6NUKldsdvdpw3jIGhMz1cqJ+9ArczJ7cx3GIwk PX8WirWmF4DG/A/CFrnhy+HE2KQsK+ZRlZFYc32HeYG6Tbh2C++BzOTYyxkUXmkEOi0k xTt2rad3nwG1/HXaM/GIW7ndJd+xF1vxwoL77XDNGhT/4l0+wVpZ2QhQn6ruUQVtS02g ux2w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=jAnZHwKItrjXdvdR58QzqOoGM6YiK6Tg67ZIO3IEXZQ=; b=TTPfMM13Pu9OMkt7JxxQcBfbqEEvjOOoD3OhDR9jjNMI3rOH3FU9JWaJ0i279B6ENc afd6v9+JHkBxdfK2LuuX0Xs1oozl+ODcj9U2gDDA2zlJqO4d6n1q3VEnYaTy47VQDl32 PaiDPLLKTvPmffe5ANx4wHYxaanegVYtFUwxf2G0LRmMkRVDwTjOHZoJ0qe89+WdW2y2 KqCv97hIG/ksaGLxClZ5TRxd2e526HyQJf4Fqp8BUpcWZzcGHL6EdQWVen1qZVLC94lU dPfPSUpdAOrdOOSErXE5OGN36zxwBIFEHg6h9UvYsdx8GyRVIw4kEW25Vc//14hdrd9M cxHg== X-Gm-Message-State: AOAM530JJcsyGeEvUzWUBBrJC099TNgwOteWgIcuS7ccgTYC2a182LsF uc/0L24eMtPD9JUxlnL8tW4= X-Google-Smtp-Source: ABdhPJzGSWcXsTvrFChy/oKLxWzAYTmdg9pUBz7YXxu/sHbxaHPFNUziq5MLvb9Mv5LaLwHDPyG+XA== X-Received: by 2002:a17:907:4064:: with SMTP id nl4mr4903112ejb.342.1596728106880; Thu, 06 Aug 2020 08:35:06 -0700 (PDT) Received: from gmail.com (54033286.catv.pool.telekom.hu. [84.3.50.134]) by smtp.gmail.com with ESMTPSA id h9sm4027593ejt.50.2020.08.06.08.35.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Aug 2020 08:35:06 -0700 (PDT) Date: Thu, 6 Aug 2020 17:35:00 +0200 From: Ingo Molnar To: Dan Williams Cc: kernel test robot , 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: <20200806153500.GC2131635@gmail.com> References: <159630256804.3143511.8894023468833792004.stgit@dwillia2-desk3.amr.corp.intel.com> <20200803094257.GA23458@shao2-debian> <20200806133452.GA2077191@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * 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. Thanks, Ingo