From: Bill Wendling <morbo@google.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <natechancellor@gmail.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>,
Sami Tolvanen <samitolvanen@google.com>
Subject: Re: [PATCH] pgo: add clang's Profile Guided Optimization infrastructure
Date: Mon, 11 Jan 2021 13:32:43 -0800 [thread overview]
Message-ID: <CAGG=3QVpxUpZJJYiy88YYk80-kvRPipnYdk9_9WzN=bToX9POA@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdnssY=CV4daRQvGa659AzGvMT+Kb10g5-DDuZjqbp-J5A@mail.gmail.com>
On Mon, Jan 11, 2021 at 1:18 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Mon, Jan 11, 2021 at 1:04 PM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > On Mon, Jan 11, 2021 at 12:18:21AM -0800, Bill Wendling 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 be used either by the compiler if LTO isn't enabled:
> > >
> > > ... -fprofile-use=vmlinux.profdata ...
> > >
> > > or by LLD if LTO is enabled:
> > >
> > > ... -lto-cs-profile-file=vmlinux.profdata ...
> > >
> > > This initial submission is restricted to x86, as that's the platform we 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.
> > >
> > > [1] https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization
> > >
> > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> > > Co-developed-by: Bill Wendling <morbo@google.com>
> > > Signed-off-by: Bill Wendling <morbo@google.com>
> >
> > I took this for a spin against x86_64_defconfig and ran into two issues:
> >
> > 1. https://github.com/ClangBuiltLinux/linux/issues/1252
>
> "Cannot split an edge from a CallBrInst"
> Looks like that should be fixed first, then we should gate this
> feature on clang-12.
>
Weird. I'll investigate.
> >
> > There is also one in drivers/gpu/drm/i915/i915_query.c. For the time
> > being, I added PGO_PROFILE_... := n for those two files.
> >
> > 2. After doing that, I run into an undefined function error with ld.lld.
> >
> > How I tested:
> >
> > $ make -skj"$(nproc)" LLVM=1 defconfig
> >
> > $ scripts/config -e PGO_CLANG
> >
> > $ make -skj"$(nproc)" LLVM=1 olddefconfig vmlinux all
> > ld.lld: error: undefined symbol: __llvm_profile_instrument_memop
>
> Err...that seems like it should be implemented in
> kernel/pgo/instrument.c in this patch in a v2?
>
Yes. I'll submit a new V2 with this and other feedback integrated.
> > >>> referenced by head64.c
> > >>> arch/x86/kernel/head64.o:(__early_make_pgtable)
> > >>> referenced by head64.c
> > >>> arch/x86/kernel/head64.o:(x86_64_start_kernel)
> > >>> referenced by head64.c
> > >>> arch/x86/kernel/head64.o:(copy_bootdata)
> > >>> referenced 2259 more times
> >
> > Local diff:
> >
> > diff --git a/drivers/char/Makefile b/drivers/char/Makefile
> > index ffce287ef415..4b2f238770b5 100644
> > --- a/drivers/char/Makefile
> > +++ b/drivers/char/Makefile
> > @@ -4,6 +4,7 @@
> > #
> >
> > obj-y += mem.o random.o
> > +PGO_PROFILE_random.o := n
> > obj-$(CONFIG_TTY_PRINTK) += ttyprintk.o
> > obj-y += misc.o
> > obj-$(CONFIG_ATARI_DSP56K) += dsp56k.o
> > diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> > index e5574e506a5c..d83cacc79b1a 100644
> > --- a/drivers/gpu/drm/i915/Makefile
> > +++ b/drivers/gpu/drm/i915/Makefile
> > @@ -168,6 +168,7 @@ i915-y += \
> > i915_vma.o \
> > intel_region_lmem.o \
> > intel_wopcm.o
> > +PGO_PROFILE_i915_query.o := n
> >
> > # general-purpose microcontroller (GuC) support
> > i915-y += gt/uc/intel_uc.o \
>
> I'd rather have these both sorted out before landing with PGO disabled
> on these files.
>
Agreed.
-bw
next prev parent reply other threads:[~2021-01-11 21:33 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 [this message]
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
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
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