From: Dan Aloni <dan@kernelim.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Tom Stellard <tstellar@redhat.com>,
Masahiro Yamada <masahiroy@kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Fangrui Song <maskray@google.com>,
Serge Guelton <sguelton@redhat.com>,
Sylvestre Ledru <sylvestre@mozilla.com>
Subject: Re: Very slow clang kernel config ..
Date: Sun, 2 May 2021 08:19:09 +0300 [thread overview]
Message-ID: <20210502051909.pac2pycninc7fl53@gmail.com> (raw)
In-Reply-To: <CAKwvOdk0nxxUATg2jEKgx4HutXCMXcW92SX3DT+uCTgqBwQHBg@mail.gmail.com>
On Fri, Apr 30, 2021 at 06:48:11PM -0700, Nick Desaulniers wrote:
> On Fri, Apr 30, 2021 at 6:22 PM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> > 0.92% libLLVM-12.so llvm::StringMapImpl::LookupBucketFor
>
> ^ wait a minute; notice how in your profile the `Shared Object` is
> attributed to `libLLVM-12.so` while mine is `clang-13`? Clang can be
> built as either having libllvm statically linked or dynamically; see
> the cmake variables
> LLVM_BUILD_LLVM_DYLIB:BOOL
> LLVM_LINK_LLVM_DYLIB:BOOL
> BUILD_SHARED_LIBS:BOOL
> https://llvm.org/docs/CMake.html
>
> I think those are frowned upon; useful for cutting down on developers
> iteration speed due to not having to relink llvm when developing
> clang. But shipping that in production? I just checked and it doesn't
> look like we do that for AOSP's build of LLVM.
There's also `-DLLVM_ENABLE_LTO=Thin` that enables LTO for building LLVM
and Clang themselves, considered they can be bootstrapped like this
using a previous version of Clang. Combining that with a non-shared
library build mode for both Clang and LLVM, the result is possibly the
fastest and most optimized build that is achievable. Unfortunately I
see distributions neglecting to enable this in packaging this as well.
On a side note, I'm also a Fedora user and agree with Linus about this.
I'd like to see an opt-in bypass of the shared library policy via
something like `dnf install clang-optimized` that would install the
fastest and most optimized Clang build regardless of RPM install size.
--
Dan Aloni
next prev parent reply other threads:[~2021-05-02 5:19 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 21:53 Very slow clang kernel config Linus Torvalds
2021-04-30 0:19 ` Nick Desaulniers
2021-04-30 2:22 ` Nick Desaulniers
2021-05-01 0:19 ` Nick Desaulniers
2021-05-01 0:23 ` Nick Desaulniers
2021-05-01 0:25 ` Nick Desaulniers
2021-05-01 0:40 ` Nick Desaulniers
2021-05-01 1:22 ` Linus Torvalds
2021-05-01 1:48 ` Nick Desaulniers
2021-05-01 2:16 ` Fangrui Song
2021-05-01 3:32 ` Tom Stellard
2021-05-01 16:32 ` Linus Torvalds
2021-05-01 19:57 ` Serge Guelton
2021-05-01 22:39 ` Linus Torvalds
2021-05-01 23:55 ` Fangrui Song
2021-05-01 21:58 ` David Laight
2021-05-02 9:31 ` Adrian Bunk
2021-05-02 11:35 ` David Laight
2021-05-02 16:12 ` Linus Torvalds
2021-05-02 16:45 ` Adrian Bunk
2021-05-02 16:49 ` Linus Torvalds
2021-05-02 17:55 ` Adrian Bunk
2021-05-02 17:59 ` Linus Torvalds
2021-05-02 21:48 ` Adrian Bunk
2021-05-04 22:02 ` Miguel Ojeda
2021-05-05 0:58 ` Theodore Ts'o
2021-05-05 17:21 ` Miguel Ojeda
2021-05-04 21:32 ` Miguel Ojeda
2021-05-05 11:05 ` David Laight
2021-05-05 13:53 ` Miguel Ojeda
2021-05-05 14:13 ` David Laight
2021-05-05 16:06 ` Miguel Ojeda
2021-05-05 16:25 ` David Laight
2021-05-05 17:55 ` Miguel Ojeda
2021-05-03 1:03 ` Maciej W. Rozycki
2021-05-03 14:38 ` Theodore Ts'o
2021-05-03 14:54 ` Theodore Ts'o
2021-05-03 17:14 ` Maciej W. Rozycki
2021-05-03 16:09 ` David Laight
2021-05-04 23:04 ` Greg Stark
2021-05-05 0:55 ` Theodore Ts'o
2021-05-01 23:37 ` Mike Hommey
2021-05-02 5:19 ` Dan Aloni [this message]
2021-05-03 16:48 ` Tom Stellard
2021-05-03 19:00 ` Fangrui Song
2021-04-30 0:52 ` Nathan Chancellor
2021-04-30 2:21 ` Nick Desaulniers
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