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Date: Wed, 13 Jan 2021 20:07:10 -0800 From: Nick Desaulniers <ndesaulniers@...gle.com> To: Nathan Chancellor <natechancellor@...il.com> Cc: Bill Wendling <morbo@...gle.com>, Jonathan Corbet <corbet@....net>, Masahiro Yamada <masahiroy@...nel.org>, Linux Doc Mailing List <linux-doc@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>, clang-built-linux <clang-built-linux@...glegroups.com>, Andrew Morton <akpm@...ux-foundation.org>, Sami Tolvanen <samitolvanen@...gle.com> Subject: Re: [PATCH v4] pgo: add clang's Profile Guided Optimization infrastructure On Wed, Jan 13, 2021 at 12:55 PM Nathan Chancellor <natechancellor@...il.com> wrote: > > However, I see an issue with actually using the data: > > $ sudo -s > # mount -t debugfs none /sys/kernel/debug > # cp -a /sys/kernel/debug/pgo/profraw vmlinux.profraw > # chown nathan:nathan vmlinux.profraw > # exit > $ tc-build/build/llvm/stage1/bin/llvm-profdata merge --output=vmlinux.profdata vmlinux.profraw > warning: vmlinux.profraw: Invalid instrumentation profile data (bad magic) > error: No profiles could be merged. > > Am I holding it wrong? :) Note, this is virtualized, I do not have any > "real" x86 hardware that I can afford to test on right now. Same. I think the magic calculation in this patch may differ from upstream llvm: https://github.com/llvm/llvm-project/blob/49142991a685bd427d7e877c29c77371dfb7634c/llvm/include/llvm/ProfileData/SampleProf.h#L96-L101 vs this patch: + * Note: These internal LLVM definitions must match the compiler version. + * See llvm/include/llvm/ProfileData/InstrProfData.inc in LLVM's source code. + */ + +#ifdef CONFIG_64BIT + #define LLVM_PRF_MAGIC \ + ((u64)255 << 56 | \ + (u64)'l' << 48 | \ + (u64)'p' << 40 | \ + (u64)'r' << 32 | \ + (u64)'o' << 24 | \ + (u64)'f' << 16 | \ + (u64)'r' << 8 | \ + (u64)129) +#else + #define LLVM_PRF_MAGIC \ + ((u64)255 << 56 | \ + (u64)'l' << 48 | \ + (u64)'p' << 40 | \ + (u64)'r' << 32 | \ + (u64)'o' << 24 | \ + (u64)'f' << 16 | \ + (u64)'R' << 8 | \ + (u64)129) +#endif -- Thanks, ~Nick Desaulniers
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