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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 X-Spamd-Result: default: False [3.60 / 9.00]; IRL_BL_25(2.00)[52.25.139.140:received]; SUBJECT_HAS_UNDERSCORES(1.00)[]; MV_CASE(0.50)[]; MIME_GOOD(-0.10)[text/plain]; BAD_REP_POLICIES(0.10)[]; RCVD_NO_TLS_LAST(0.10)[]; BAYES_HAM(-0.00)[32.95%]; RCPT_COUNT_TWELVE(0.00)[14]; TO_MATCH_ENVRCPT_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; DKIM_TRACE(0.00)[linux-foundation.org:+]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_THREE(0.00)[3]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; DMARC_NA(0.00)[linux-foundation.org]; ARC_NA(0.00)[]; R_DKIM_ALLOW(0.00)[linux-foundation.org:s=korg]; MID_RHS_MATCH_FROM(0.00)[]; FROM_HAS_DN(0.00)[]; R_SPF_ALLOW(0.00)[+a:dfw.source.kernel.org]; TO_DN_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[] X-Rspamd-Queue-Id: E7D9B40014 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: owzeat9offogakr7ne5e7tircn6nuzed X-HE-Tag: 1669929760-290582 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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.