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 CA6A2C43217 for ; Thu, 1 Dec 2022 18:34:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230202AbiLASeL (ORCPT ); Thu, 1 Dec 2022 13:34:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60264 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229515AbiLASeJ (ORCPT ); Thu, 1 Dec 2022 13:34:09 -0500 Received: from wp530.webpack.hosteurope.de (wp530.webpack.hosteurope.de [80.237.130.52]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 427532EF43 for ; Thu, 1 Dec 2022 10:34:08 -0800 (PST) Received: from [2a02:8108:963f:de38:eca4:7d19:f9a2:22c5]; authenticated by wp530.webpack.hosteurope.de running ExIM with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) id 1p0oNj-00029Z-Ez; Thu, 01 Dec 2022 19:33:59 +0100 Message-ID: Date: Thu, 1 Dec 2022 19:33:58 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Subject: Re: [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression Content-Language: en-US, de-DE To: Rik van Riel , Andrew Morton , Yang Shi Cc: "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 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> From: Thorsten Leemhuis In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-bounce-key: webpack.hosteurope.de;regressions@leemhuis.info;1669919648;d0e59f7a; X-HE-SMSGID: 1p0oNj-00029Z-Ez Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? Yang Shi, Andrew, what's your option on this? I ask you directly, because it looks like Rik hasn't posted anything to lists archived on lore during the last few weeks. :-/ Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) P.S.: As the Linux kernel's regression tracker I deal with a lot of reports and sometimes miss something important when writing mails like this. If that's the case here, don't hesitate to tell me in a public reply, it's in everyone's interest to set the public record straight. > On Thu, Oct 20, 2022 at 10:16:20AM -0700, Nathan Chancellor wrote: >> On Thu, Oct 20, 2022 at 11:28:16AM -0400, Rik van Riel wrote: >>> On Thu, 2022-10-20 at 13:07 +0800, Huang, Ying wrote: >>>> Nathan Chancellor writes: >>>>> >>>>> For what it's worth, I just bisected a massive and visible >>>>> performance >>>>> regression on my Threadripper 3990X workstation to commit >>>>> f35b5d7d676e >>>>> ("mm: align larger anonymous mappings on THP boundaries"), which >>>>> seems >>>>> directly related to this report/analysis. I initially noticed this >>>>> because my full set of kernel builds against mainline went from 2 >>>>> hours >>>>> and 20 minutes or so to over 3 hours. Zeroing in on x86_64 >>>>> allmodconfig, >>>>> which I used for the bisect: >>>>> >>>>> @ 7b5a0b664ebe ("mm/page_ext: remove unused variable in >>>>> offline_page_ext"): >>>>> >>>>> Benchmark 1: make -skj128 LLVM=1 allmodconfig all >>>>>   Time (mean ± σ):     318.172 s ±  0.730 s    [User: 31750.902 s, >>>>> System: 4564.246 s] >>>>>   Range (min … max):   317.332 s … 318.662 s    3 runs >>>>> >>>>> @ f35b5d7d676e ("mm: align larger anonymous mappings on THP >>>>> boundaries"): >>>>> >>>>> Benchmark 1: make -skj128 LLVM=1 allmodconfig all >>>>> Time (mean ± σ): 406.688 s ± 0.676 s [User: 31819.526 s, >>> System: 16327.022 s] >>>>> Range (min … max): 405.954 s … 407.284 s 3 run >>>> >>>> Have you tried to build with gcc?  Want to check whether is this >>>> clang >>>> specific issue or not. >>> >>> This may indeed be something LLVM specific. In previous tests, >>> GCC has generally seen a benefit from increased THP usage. >>> Many other applications also benefit from getting more THPs. >> >> Indeed, GCC builds actually appear to be slightly faster on my system now, >> apologies for not trying that before reporting :/ >> >> 7b5a0b664ebe: >> >> Benchmark 1: make -skj128 allmodconfig all >> Time (mean ± σ): 355.294 s ± 0.931 s [User: 33620.469 s, System: 6390.064 s] >> Range (min … max): 354.571 s … 356.344 s 3 runs >> >> f35b5d7d676e: >> >> Benchmark 1: make -skj128 allmodconfig all >> Time (mean ± σ): 347.400 s ± 2.029 s [User: 34389.724 s, System: 4603.175 s] >> Range (min … max): 345.815 s … 349.686 s 3 runs >> >>> LLVM showing 10% system time before this change, and a whopping >>> 30% system time after that change, suggests that LLVM is behaving >>> quite differently from GCC in some ways. >> >> The above tests were done with GCC 12.2.0 from Arch Linux. The previous LLVM >> tests were done with a self-compiled version of LLVM from the main branch >> (16.0.0), optimized with BOLT [1]. To eliminate that as a source of issues, I >> used my distribution's version of clang (14.0.6) and saw similar results as >> before: >> >> 7b5a0b664ebe: >> >> Benchmark 1: make -skj128 LLVM=/usr/bin/ allmodconfig all >> Time (mean ± σ): 462.517 s ± 1.214 s [User: 48544.240 s, System: 5586.212 s] >> Range (min … max): 461.115 s … 463.245 s 3 runs >> >> f35b5d7d676e: >> >> Benchmark 1: make -skj128 LLVM=/usr/bin/ allmodconfig all >> Time (mean ± σ): 547.927 s ± 0.862 s [User: 47913.709 s, System: 17682.514 s] >> Range (min … max): 547.429 s … 548.922 s 3 runs >> >>> If we can figure out what these differences are, maybe we can >>> just fine tune the code to avoid this issue. >>> >>> I'll try to play around with LLVM compilation a little bit next >>> week, to see if I can figure out what might be going on. I wonder >>> if LLVM is doing lots of mremap calls or something... >> >> If there is any further information I can provide or patches I can test, >> I am more than happy to do so. >> >> [1]: https://github.com/llvm/llvm-project/tree/96552e73900176d65ee6650facae8d669d6f9498/bolt > > Was there ever a follow up to this report that I missed? I just > noticed that I am still reverting f35b5d7d676e in my mainline kernel. > > Cheers, > Nathan > #regzbot ignore-activity