LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Tom Stellard <tstellar@redhat.com>
To: Dan Aloni <dan@kernelim.com>, Nick Desaulniers <ndesaulniers@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	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: Mon, 3 May 2021 09:48:57 -0700
Message-ID: <6c4febd7-f826-9935-4163-138b1fed8278@redhat.com> (raw)
In-Reply-To: <20210502051909.pac2pycninc7fl53@gmail.com>

On 5/1/21 10:19 PM, Dan Aloni wrote:
> 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.
> 

I have experimented with creating a static version of clang in the past,
but never really found a solution I liked enough to upstream into Fedora.
e.g. This solution[1] that we're using to bootstrap clang in our internal
clang-as-the-default-cc Fedora buildroots that we use for testing.

If someone could file a bug[2] against the clang package in Fedora (or RHEL even)
with some data or other information that shows the downsides of the shared
build of of clang, that would be really helpful.

-Tom

[1] https://src.fedoraproject.org/fork/tstellar/rpms/clang/c/dea2413c6822cc7aa7a08ebe73d10abf8216259f?branch=clang-minimal
[2] https://bugzilla.redhat.com/


  reply index

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-29 21:53 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
2021-05-03 16:48                 ` Tom Stellard [this message]
2021-05-03 19:00                   ` Fangrui Song
2021-04-30  0:52 ` Nathan Chancellor
2021-04-30  2:21   ` Nick Desaulniers

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=6c4febd7-f826-9935-4163-138b1fed8278@redhat.com \
    --to=tstellar@redhat.com \
    --cc=clang-built-linux@googlegroups.com \
    --cc=dan@kernelim.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=masahiroy@kernel.org \
    --cc=maskray@google.com \
    --cc=nathan@kernel.org \
    --cc=ndesaulniers@google.com \
    --cc=sguelton@redhat.com \
    --cc=sylvestre@mozilla.com \
    --cc=torvalds@linux-foundation.org \
    /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

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git
	git clone --mirror https://lore.kernel.org/lkml/10 lkml/git/10.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git