From: "Fāng-ruì Sòng" <maskray@google.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Bill Wendling <morbo@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Masahiro Yamada <masahiroy@kernel.org>,
Linux Doc Mailing List <linux-doc@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Andrew Morton <akpm@linux-foundation.org>,
Nathan Chancellor <natechancellor@gmail.com>,
Sami Tolvanen <samitolvanen@google.com>,
Alistair Delva <adelva@google.com>
Subject: Re: [PATCH v2] pgo: add clang's Profile Guided Optimization infrastructure
Date: Tue, 12 Jan 2021 09:45:17 -0800 [thread overview]
Message-ID: <CAFP8O3J+85x2S+9T2vM+iem=t45MdJt+D1houpqKGhDRfcHu-w@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdk+NqhzC_4wFbQMJmLMQWoDSjQiRJyCGe5dsWkqK_NJJQ@mail.gmail.com>
On Tue, Jan 12, 2021 at 9:37 AM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
>
> On Mon, Jan 11, 2021 at 9:14 PM Bill Wendling <morbo@google.com> wrote:
> >
> > From: Sami Tolvanen <samitolvanen@google.com>
> >
> > Enable the use of clang's Profile-Guided Optimization[1]. To generate a
> > profile, the kernel is instrumented with PGO counters, a representative
> > workload is run, and the raw profile data is collected from
> > /sys/kernel/debug/pgo/profraw.
> >
> > The raw profile data must be processed by clang's "llvm-profdata" tool
> > before it can be used during recompilation:
> >
> > $ cp /sys/kernel/debug/pgo/profraw vmlinux.profraw
> > $ llvm-profdata merge --output=vmlinux.profdata vmlinux.profraw
> >
> > Multiple raw profiles may be merged during this step.
> >
> > The data can now be used by the compiler:
> >
> > $ make LLVM=1 KCFLAGS=-fprofile-use=vmlinux.profdata ...
> >
> > This initial submission is restricted to x86, as that's the platform we
>
> Please drop all changes to arch/* that are not to arch/x86/ then; we
> can cross that bridge when we get to each arch. For example, there's
> no point disabling PGO for architectures LLVM doesn't even have a
> backend for.
>
> > know works. This restriction can be lifted once other platforms have
> > been verified to work with PGO.
> >
> > Note that this method of profiling the kernel is clang-native and isn't
> > compatible with clang's gcov support in kernel/gcov.
>
> Then the Kconfig option should depend on !GCOV so that they are
> mutually exclusive and can't be selected together accidentally; such
> as by bots doing randconfig tests.
The profile formats (Clang PGO, Clang gcov, GCC gcov/PGO) are
different but Clang PGO can be used with Clang's gcov implementation:
clang -fprofile-generate --coverage a.cc; ./a.out => default*.profraw + a.gcda
> <large snip>
>
> > +static inline int inst_prof_popcount(unsigned long long value)
> > +{
> > + value = value - ((value >> 1) & 0x5555555555555555ULL);
> > + value = (value & 0x3333333333333333ULL) +
> > + ((value >> 2) & 0x3333333333333333ULL);
> > + value = (value + (value >> 4)) & 0x0F0F0F0F0F0F0F0FULL;
> > +
> > + return (int)((unsigned long long)(value * 0x0101010101010101ULL) >> 56);
> > +}
>
> The kernel has a portable popcnt implementation called hweight64 if
> you #include <asm-generic/bitops/hweight.h>; does that work here?
> https://en.wikipedia.org/wiki/Hamming_weight
> --
> Thanks,
> ~Nick Desaulniers
>
> --
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/CAKwvOdk%2BNqhzC_4wFbQMJmLMQWoDSjQiRJyCGe5dsWkqK_NJJQ%40mail.gmail.com.
next prev parent reply other threads:[~2021-01-12 17:46 UTC|newest]
Thread overview: 123+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 8:18 [PATCH] pgo: add clang's Profile Guided Optimization infrastructure Bill Wendling
2021-01-11 8:39 ` Sedat Dilek
2021-01-11 8:42 ` Sedat Dilek
2021-01-11 9:17 ` Bill Wendling
2021-01-11 9:57 ` Sedat Dilek
2021-01-11 18:28 ` Nathan Chancellor
2021-01-11 20:12 ` Fangrui Song
2021-01-11 20:23 ` Bill Wendling
2021-01-11 20:31 ` Fangrui Song
2021-01-12 0:37 ` Bill Wendling
2021-01-12 0:44 ` Fāng-ruì Sòng
2021-01-11 21:04 ` Nathan Chancellor
2021-01-11 21:17 ` Nick Desaulniers
2021-01-11 21:32 ` Bill Wendling
2021-01-12 5:14 ` [PATCH v2] " Bill Wendling
2021-01-12 5:17 ` Sedat Dilek
2021-01-12 5:31 ` [PATCH v3] " Bill Wendling
2021-01-12 9:10 ` kernel test robot
2021-01-12 9:10 ` kernel test robot
2021-01-12 17:22 ` Nathan Chancellor
2021-01-13 6:19 ` [PATCH v4] " Bill Wendling
2021-01-13 20:55 ` Nathan Chancellor
2021-01-13 21:59 ` Bill Wendling
2021-01-14 4:07 ` Nick Desaulniers
2021-01-16 0:01 ` Nick Desaulniers
2021-01-16 0:13 ` Nick Desaulniers
2021-01-16 4:30 ` Sedat Dilek
2021-01-16 5:07 ` Sedat Dilek
2021-01-16 5:18 ` Sedat Dilek
2021-01-18 0:57 ` Sedat Dilek
2021-01-13 23:01 ` Nick Desaulniers
2021-01-16 9:43 ` [PATCH v5] " Bill Wendling
2021-01-16 17:38 ` Sedat Dilek
2021-01-16 18:36 ` Sedat Dilek
2021-01-16 20:23 ` Bill Wendling
2021-01-17 10:44 ` Sedat Dilek
2021-01-17 10:53 ` Sedat Dilek
2021-01-17 11:23 ` Sedat Dilek
2021-01-17 11:42 ` Sedat Dilek
2021-01-17 11:58 ` Sedat Dilek
2021-01-17 12:05 ` Sedat Dilek
2021-01-17 17:42 ` Sedat Dilek
2021-01-17 20:34 ` Bill Wendling
2021-01-17 23:33 ` Sedat Dilek
2021-01-18 0:26 ` Sedat Dilek
2021-01-18 2:32 ` Bill Wendling
2021-01-18 12:39 ` Sedat Dilek
2021-01-18 17:26 ` Sedat Dilek
2021-01-18 21:56 ` Bill Wendling
2021-01-18 23:29 ` Sedat Dilek
2021-01-21 2:03 ` Sedat Dilek
2021-01-21 22:44 ` Sedat Dilek
2021-01-22 1:42 ` Nick Desaulniers
2021-01-22 1:49 ` Sedat Dilek
2021-01-22 1:52 ` Nick Desaulniers
2021-01-22 1:54 ` Sedat Dilek
2021-01-20 1:02 ` Nick Desaulniers
2021-01-21 0:51 ` Nick Desaulniers
2021-01-21 8:24 ` Bill Wendling
2021-01-21 8:24 ` [PATCH v6] " Bill Wendling
2021-01-21 10:34 ` Sedat Dilek
2021-01-22 1:44 ` Nick Desaulniers
2021-01-22 1:51 ` Sedat Dilek
2021-01-22 0:14 ` Sedat Dilek
2021-01-22 0:58 ` Sedat Dilek
2021-01-22 1:29 ` Nick Desaulniers
2021-01-22 10:11 ` [PATCH v7] " Bill Wendling
2021-01-22 11:31 ` Sedat Dilek
2021-01-22 18:41 ` Nick Desaulniers
2021-01-28 20:46 ` Sedat Dilek
2021-01-28 21:12 ` Nick Desaulniers
2021-01-28 21:19 ` Sedat Dilek
2021-01-28 21:24 ` Nick Desaulniers
2021-01-28 21:39 ` Sedat Dilek
2021-01-29 7:43 ` Sedat Dilek
2021-01-29 21:48 ` Nick Desaulniers
2021-02-10 23:25 ` Bill Wendling
2021-02-22 21:52 ` Bill Wendling
2021-02-26 22:20 ` [PATCH v8] " Bill Wendling
2021-02-26 22:55 ` Bill Wendling
2021-02-28 18:52 ` Fangrui Song
2021-02-28 21:50 ` Fangrui Song
2021-01-12 17:37 ` [PATCH v2] " Nick Desaulniers
2021-01-12 17:45 ` Fāng-ruì Sòng [this message]
2021-01-21 2:21 ` [PATCH] " Sedat Dilek
2021-01-22 1:34 ` Nick Desaulniers
2021-01-22 1:43 ` Sedat Dilek
2021-04-07 21:17 ` [PATCH v9] " Bill Wendling
2021-04-07 21:22 ` Kees Cook
2021-04-07 21:44 ` Fāng-ruì Sòng
2021-04-07 21:47 ` Nathan Chancellor
2021-04-07 21:58 ` Bill Wendling
2021-05-19 21:37 ` Kees Cook
2021-05-22 23:51 ` Bill Wendling
2021-05-31 21:12 ` Nathan Chancellor
2021-06-01 17:31 ` Nick Desaulniers
2021-06-12 16:59 ` Peter Zijlstra
2021-06-12 17:25 ` Bill Wendling
2021-06-12 18:15 ` Peter Zijlstra
2021-06-12 19:10 ` Bill Wendling
2021-06-12 19:28 ` Bill Wendling
2021-06-12 20:25 ` Peter Zijlstra
2021-06-12 20:56 ` Bill Wendling
2021-06-12 22:47 ` Bill Wendling
2021-06-13 18:07 ` Bill Wendling
2021-06-14 9:43 ` Peter Zijlstra
2021-06-14 10:18 ` Peter Zijlstra
2021-06-14 7:51 ` Peter Zijlstra
2021-06-14 9:01 ` Peter Zijlstra
2021-06-14 9:39 ` Bill Wendling
2021-06-14 10:44 ` Peter Zijlstra
2021-06-14 11:41 ` Bill Wendling
2021-06-14 11:43 ` Bill Wendling
2021-06-14 14:16 ` Marco Elver
2021-06-14 15:26 ` Kees Cook
2021-06-14 15:35 ` Peter Zijlstra
2021-06-14 16:22 ` Kees Cook
2021-06-14 18:07 ` Nick Desaulniers
2021-06-14 20:49 ` Nick Desaulniers
2021-06-14 15:46 ` Peter Zijlstra
2021-06-14 16:03 ` Nick Desaulniers
2021-06-12 20:20 ` Fangrui Song
2021-06-12 20:31 ` Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAFP8O3J+85x2S+9T2vM+iem=t45MdJt+D1houpqKGhDRfcHu-w@mail.gmail.com' \
--to=maskray@google.com \
--cc=adelva@google.com \
--cc=akpm@linux-foundation.org \
--cc=clang-built-linux@googlegroups.com \
--cc=corbet@lwn.net \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kbuild@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=masahiroy@kernel.org \
--cc=morbo@google.com \
--cc=natechancellor@gmail.com \
--cc=ndesaulniers@google.com \
--cc=samitolvanen@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.