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charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: B68D0140004 X-Stat-Signature: yob8d1kkudb7yn689ehxzpauca37mc6g X-Rspamd-Server: rspam01 X-Spamd-Result: default: False [4.08 / 9.00]; SORBS_IRL_BL(3.00)[209.85.215.175:from]; SUBJECT_HAS_UNDERSCORES(1.00)[]; BAD_REP_POLICIES(0.10)[]; MIME_GOOD(-0.10)[text/plain]; RCVD_NO_TLS_LAST(0.10)[]; BAYES_HAM(-0.02)[51.86%]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; DMARC_POLICY_ALLOW(0.00)[gmail.com,none]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_TWELVE(0.00)[14]; DKIM_TRACE(0.00)[gmail.com:+]; TO_MATCH_ENVRCPT_SOME(0.00)[]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; FROM_HAS_DN(0.00)[]; R_DKIM_ALLOW(0.00)[gmail.com:s=20210112]; MID_RHS_MATCH_FROMTLD(0.00)[]; TO_DN_SOME(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[linux-mm@kvack.org]; R_SPF_ALLOW(0.00)[+ip4:209.85.128.0/17:c]; ARC_NA(0.00)[] X-HE-Tag: 1669931109-861550 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, Dec 1, 2022 at 1:22 PM Andrew Morton wrote: > > 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. +1 > >