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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DEA09C4708D for ; Thu, 1 Dec 2022 21:22:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230468AbiLAVWo (ORCPT ); Thu, 1 Dec 2022 16:22:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44710 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229793AbiLAVWm (ORCPT ); Thu, 1 Dec 2022 16:22:42 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 414552316F for ; Thu, 1 Dec 2022 13:22:40 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C09FB62129 for ; Thu, 1 Dec 2022 21:22:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B9BAC433D6; Thu, 1 Dec 2022 21:22:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1669929759; bh=GIsKWp+Z1ekqEUas+5otTGGZ0St38k31vgjqrcnxpmE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ezNAOPx5mJeTaeYSxoCj90/+zMNm6SMoJqzDe1achx9NeQ5aiExRrBPoGbifDVlkO pQADvDcok3kxJbGNmwPaggm1laXkxugF8AaKOyZpf1E6q/Ti7UvtcO91u82++JyrtI A++mK2NytQbcbxl8sYa0kzZc58Fl3r2xKlSKPtXA= Date: Thu, 1 Dec 2022 13:22:37 -0800 From: Andrew Morton To: Rik van Riel Cc: Thorsten Leemhuis , Yang Shi , "Huang, Ying" , kernel test robot , lkp@lists.01.org, lkp@intel.com, Matthew Wilcox , linux-kernel@vger.kernel.org, linux-mm@kvack.org, feng.tang@intel.com, zhengjun.xing@linux.intel.com, fengwei.yin@intel.com, Nathan Chancellor Subject: Re: [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression Message-Id: <20221201132237.c55c4bd07ba44463b146882e@linux-foundation.org> In-Reply-To: <07adee081a70c2b4b44d9bf93a0ad3142e091086.camel@surriel.com> References: <202210181535.7144dd15-yujie.liu@intel.com> <87edv4r2ip.fsf@yhuang6-desk2.ccr.corp.intel.com> <871qr3nkw2.fsf@yhuang6-desk2.ccr.corp.intel.com> <366045a27a96e01d0526d63fd78d4f3c5d1f530b.camel@surriel.com> <07adee081a70c2b4b44d9bf93a0ad3142e091086.camel@surriel.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 01 Dec 2022 15:29:41 -0500 Rik van Riel wrote: > On Thu, 2022-12-01 at 19:33 +0100, Thorsten Leemhuis wrote: > > Hi, this is your Linux kernel regression tracker. > > > > On 28.11.22 07:40, Nathan Chancellor wrote: > > > Hi Rik, > > > > I wonder what we should do about below performance regression. Is > > reverting the culprit now and reapplying it later together with a fix > > a > > viable option? Or was anything done/is anybody doing something > > already > > to address the problem and I just missed it? > > The changeset in question speeds up kernel compiles with > GCC, as well as the runtime speed of other programs, due > to being able to use THPs more. However, it slows down kernel > compiles with clang, due to ... something clang does. > > I have not figured out what that something is yet. > > I don't know if I have the wrong version of clang here, > but I have not seen any smoking gun at all when tracing > clang system calls. I see predominantly small mmap and > unmap calls, and nothing that even triggers 2MB alignment. 2.8% speedup for gcc is nice. Massive slowdown in the malloc banchmark and in LLVM/clang is very bad - we don't know what other userspace will be so affected. So I think we revert until this is fully understood.