linux-kernel - Re: [PATCH v6] pgo: add clang's Profile Guided Optimization infrastructure

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Message-ID: <CAKwvOdmmhW36Zbkc0aPLAOrP8UXsX5vKkrfWYH89sCKLmE5vuw@mail.gmail.com>
Date:   Thu, 21 Jan 2021 17:44:36 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Sedat Dilek <sedat.dilek@...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 ML <clang-built-linux@...glegroups.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: Re: [PATCH v6] pgo: add clang's Profile Guided Optimization infrastructure

On Thu, Jan 21, 2021 at 2:35 AM Sedat Dilek <sedat.dilek@...il.com> wrote:
>
> Thanks for v6.
>
> Small Changelog nits:
> * Can you reverse-order the changelog - latest v6 first.
> * v4: s/Makfile changes and se/Ma*k*efile changes and *u*se
>
> Can you add a hint to this "Clang-PGO" patch requiring Clang >= 12?
>
> Can you please add a comment for people using Clang >= 12 (ToT) and
> have kernel-modules enabled, they will need the patch from CBL issue
> #1250?
> Otherwise they cannot boot and follow the next steps in the workflow.
>
> Can you put a comment about value "1" to reset the profiling counter?
> That there is no "0" value stopping it.
>
> Can you add an example for the workload test?
> Here I do a x86-64 defconfig build.
> See attached script.
>
> Usually, I download this patch from LORE.
>
> link="https://lore.kernel.org/r/20210111081821.3041587-1-morbo@google.com"
> b4 -d am $link
>
> This downloads v6.
>
> What if I want a previous version (compare)?
> Again, I will love to see a "clang-pgo" branch and maybe tags for the
> several versions in your personal GitHub.
> Come on, Bill :-).

That's quite a long list, Sedat!  Do you think some of these can be
follow ups, once the core lands?  I'd much prefer to land the meat of
this and follow up quickly, than tire out poor Bill! :P
-- 
Thanks,
~Nick Desaulniers