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Clang Profile Guided Optimizations Support Sent In For Linux 5.14

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  • smitty3268
    replied
    Originally posted by CommunityMember View Post

    I could have sworn that Micheal stated he intended to run LTO benchmarks of the kernel after the 5.12 release.

    Update:

    Found it in https://www.phoronix.com/scan.php?pa...ang-LTO-Merged where the statement was: "I'll be running some Clang LTO kernel comparison benchmarks after the merge window has passed."
    Technically this is still after.

    Leave a comment:


  • CommunityMember
    replied
    Originally posted by Grinch View Post
    Has there been any kernel LTO benchmarks made yet ?
    I could have sworn that Micheal stated he intended to run LTO benchmarks of the kernel after the 5.12 release.

    Update:

    Found it in https://www.phoronix.com/scan.php?pa...ang-LTO-Merged where the statement was: "I'll be running some Clang LTO kernel comparison benchmarks after the merge window has passed."
    Last edited by CommunityMember; 29 June 2021, 12:34 PM. Reason: Include reference....

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  • CommunityMember
    replied
    Originally posted by sdack View Post
    Phoronix should contact Andi Kleen and ask him for a comment.
    I believe you are free to contact Andi either via a public list, or personally, and ask when (if ever) he intends to try to upstream the patches (they were rejected for cause by Linus previously). If he no longer plans to do the work to upstream, the question is whether someone else intends to do the work, or is the issue closed for now?

    Leave a comment:


  • sdack
    replied
    Originally posted by Grinch View Post
    Has there been any kernel LTO benchmarks made yet ?
    Not by Phoronix afaik. It was only reported about it in the past and benchmarks were made by Andi Kleen.

    https://www.phoronix.com/scan.php?pa...tem&px=MTE2MzY

    LTO in GCC was introduced around GCC 4.6 iirc and these early tests were made with GCC 4.7, which still had many issues to sort out. 9 years have past since then and many improvements were made. New kernel benchmarks for LTO are definitely in order, both for GCC and Clang.
    Last edited by sdack; 29 June 2021, 06:13 AM.

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  • Grinch
    replied
    Has there been any kernel LTO benchmarks made yet ?

    Leave a comment:


  • sdack
    replied
    Is there any news to report on GCC LTO support for the mainline kernel?

    The patches, which go all the way back to kernel 3.7, are still being updated and can be found here: https://git.kernel.org/pub/scm/linux...inux-misc.git/

    Phoronix should contact Andi Kleen and ask him for a comment.

    Leave a comment:


  • coder
    replied
    Next, perhaps we'll see support being wired in for runtime re-optimization of the kernel, when profiling data indicates control-flow that deviates from what the kernel was optimized for.

    Perhaps old binaries could be cached, so that if they match the current behavior well enough, they can simply be swapped in.

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  • carewolf
    replied
    DeJaVu?

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  • CochainComplex
    replied
    Super interessting. Michael do think it would be possible to checlout thia pgo feature once it is mature enough? It would also be of interesst how a "wrongly" trained profile changes the performance. ...I know that is difficult to achieve...especially repeatability.

    Leave a comment:


  • Clang Profile Guided Optimizations Support Sent In For Linux 5.14

    Phoronix: Clang Profile Guided Optimizations Support Sent In For Linux 5.14

    Compiling the Linux kernel with LLVM's Clang code compiler continues to be more featureful with plumbing now being added to handle profile-guided optimizations (PGO) to help in achieving greater performance for optimizing kernel builds for targeted workloads...

    https://www.phoronix.com/scan.php?pa...PGO-Linux-5.14
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