From: Rik van Riel <riel@surriel.com> To: "Huang, Ying" <ying.huang@intel.com>, Nathan Chancellor <nathan@kernel.org> Cc: kernel test robot <yujie.liu@intel.com>, lkp@lists.01.org, lkp@intel.com, Andrew Morton <akpm@linux-foundation.org>, Yang Shi <shy828301@gmail.com>, Matthew Wilcox <willy@infradead.org>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, feng.tang@intel.com, zhengjun.xing@linux.intel.com, fengwei.yin@intel.com Subject: Re: [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression Date: Thu, 20 Oct 2022 11:28:16 -0400 [thread overview] Message-ID: <366045a27a96e01d0526d63fd78d4f3c5d1f530b.camel@surriel.com> (raw) In-Reply-To: <871qr3nkw2.fsf@yhuang6-desk2.ccr.corp.intel.com> [-- Attachment #1: Type: text/plain, Size: 2072 bytes --] On Thu, 2022-10-20 at 13:07 +0800, Huang, Ying wrote: > > Nathan Chancellor <nathan@kernel.org> 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. 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. 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... -- All Rights Reversed. [-- Attachment #2: This is a digitally signed message part --] [-- Type: application/pgp-signature, Size: 488 bytes --]
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From: Rik van Riel <riel@surriel.com> To: lkp@lists.01.org Subject: Re: [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression Date: Thu, 20 Oct 2022 11:28:16 -0400 [thread overview] Message-ID: <366045a27a96e01d0526d63fd78d4f3c5d1f530b.camel@surriel.com> (raw) In-Reply-To: <871qr3nkw2.fsf@yhuang6-desk2.ccr.corp.intel.com> [-- Attachment #1: Type: text/plain, Size: 2072 bytes --] On Thu, 2022-10-20 at 13:07 +0800, Huang, Ying wrote: > > Nathan Chancellor <nathan@kernel.org> 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. 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. 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... -- All Rights Reversed. [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 488 bytes --]
next prev parent reply other threads:[~2022-10-20 15:30 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-10-18 8:44 [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression kernel test robot 2022-10-18 8:44 ` kernel test robot 2022-10-19 2:05 ` Huang, Ying 2022-10-19 2:05 ` Huang, Ying 2022-10-20 4:23 ` Nathan Chancellor 2022-10-20 4:23 ` Nathan Chancellor 2022-10-20 5:07 ` Huang, Ying 2022-10-20 5:07 ` Huang, Ying 2022-10-20 15:28 ` Rik van Riel [this message] 2022-10-20 15:28 ` Rik van Riel 2022-10-20 17:16 ` Nathan Chancellor 2022-10-20 17:16 ` Nathan Chancellor 2022-11-28 6:40 ` Nathan Chancellor 2022-12-01 18:33 ` Thorsten Leemhuis 2022-12-01 20:29 ` Rik van Riel 2022-12-01 21:22 ` Andrew Morton 2022-12-01 21:44 ` Yang Shi 2022-12-02 8:46 ` Thorsten Leemhuis 2022-12-02 18:44 ` Andrew Morton 2022-12-02 19:37 ` Thorsten Leemhuis 2022-12-01 21:35 ` Nathan Chancellor 2022-12-16 11:48 ` Yin, Fengwei 2022-10-20 16:40 ` Yujie Liu 2022-10-20 16:40 ` Yujie Liu 2022-11-29 8:59 ` [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression #forregzbot Thorsten Leemhuis 2022-12-02 6:43 ` Thorsten Leemhuis
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