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Shutemov" , Dave Hansen , Andy Lutomirski , x86@kernel.org, Kostya Serebryany , Andrey Ryabinin , Andrey Konovalov , Alexander Potapenko , Taras Madan , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , Bharata B Rao , Jacob Pan , Ashok Raj , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sami Tolvanen , joao@overdrivepizza.com Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: 0E077A0015 X-Rspamd-Server: rspam01 X-Stat-Signature: e6zsokyznz5ue1zeo97ce777n497cuof X-HE-Tag: 1673979994-486870 X-HE-Meta: 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 syPNDNFX Z7xiMiFqVr2GUpJmJlvpMuLTC7n/E+QE2tRkKYEEzEAqy8mPVIDDvP2qmUf54jgoZYBUw0Z+oSWdtLFRxUiZaZ/OjQ6q02FYtq9FMe4smjBZLutJqD90XlK2uD/TsEKg6Ldy7 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 Tue, Jan 17, 2023 at 9:29 AM Linus Torvalds wrote: > > On Tue, Jan 17, 2023 at 9:18 AM Linus Torvalds > wrote: > > > > The reason clang seems to generate saner code is that clang seems to > > largely ignore the whole "__builtin_expect()", at least not to the > > point where it tries to make the unlikely case be out-of-line. > > Side note: that's not something new or unusual. It's been the case > since I started testing clang - we have several code-paths where we > use "unlikely()" to try to get very unlikely cases to be out-of-line, > and clang just mostly ignores it, or treats it as a very weak hint. I > think the only way to get clang to treat it as a *strong* hint is to > use PGO. I'd be surprised if that were intentional or by design. Do you guys have a bug report we could look at? > So clang ignoring the likely() hint is probably the right thing here, > and then the wrong thing in some other places. -- Thanks, ~Nick Desaulniers