From: Arnd Bergmann <arnd@arndb.de>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Marco Elver <elver@google.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Dmitry Vyukov <dvyukov@google.com>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@google.com>,
kasan-dev <kasan-dev@googlegroups.com>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will@kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH -tip v3 09/11] data_race: Avoid nested statement expression
Date: Tue, 26 May 2020 12:42:16 +0200 [thread overview]
Message-ID: <CAK8P3a0RJtbVi1JMsfik=jkHCNFv+DJn_FeDg-YLW+ueQW3tNg@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdnR7BXw_jYS5PFTuUamcwprEnZ358qhOxSu6wSSSJhxOA@mail.gmail.com>
On Thu, May 21, 2020 at 10:21 PM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
>
> On Thu, May 21, 2020 at 7:22 AM 'Marco Elver' via Clang Built Linux
> <clang-built-linux@googlegroups.com> wrote:
> >
> > It appears that compilers have trouble with nested statement
> > expressions. Therefore remove one level of statement expression nesting
> > from the data_race() macro. This will help us avoid potential problems
> > in future as its usage increases.
> >
> > Link: https://lkml.kernel.org/r/20200520221712.GA21166@zn.tnic
> > Acked-by: Will Deacon <will@kernel.org>
> > Signed-off-by: Marco Elver <elver@google.com>
>
> Thanks Marco, I can confirm this series fixes the significant build
> time regressions.
>
> Tested-by: Nick Desaulniers <ndesaulniers@google.com>
>
> More measurements in: https://github.com/ClangBuiltLinux/linux/issues/1032
>
> Might want:
> Reported-by: Borislav Petkov <bp@suse.de>
> Reported-by: Nathan Chancellor <natechancellor@gmail.com>
> too.
I find this patch only solves half the problem: it's much faster than
without the
patch, but still much slower than the current mainline version. As far as I'm
concerned, I think the build speed regression compared to mainline is not yet
acceptable, and we should try harder.
I have not looked too deeply at it yet, but this is what I found from looking
at a file in a randconfig build:
Configuration: see https://pastebin.com/raw/R9erCwNj
== Current linux-next ==
with "data_race: Avoid nested statement expression"
and "compiler.h: Remove data_race() and unnecessary checks from
{READ,WRITE}_ONCE()"
$ touch fs/ocfs2/journal.c ; cp
../arch/x86/configs/0xFFA843AA_defconfig obj-x86/.config ; perf stat
make olddefconfig O=obj-x86/ CC=clang-11 fs/ocfs2/journal.i ARCH=x86
-skj30 ; wc obj-x86/fs/ocfs2/journal.i
48741 552950 9010050 obj-x86/fs/ocfs2/journal.i
real 0m12.514s
user 0m10.270s
sys 0m2.668s
== Same tree, without those two ==
$ touch fs/ocfs2/journal.c cp ../arch/x86/configs/0xFFA843AA_defconfig
obj-x86/.config ; time make olddefconfig O=obj-x86/ CC=clang-11
fs/ocfs2/journal.i ARCH=x86 -skj30 ; wc obj-x86/fs/ocfs2/journal.i
real 1m35.968s
user 1m33.579s
sys 0m3.523s
48741 1926607 36542560 obj-x86/fs/ocfs2/journal.i
== Mainline Linux ==
$ touch fs/ocfs2/journal.c ; cp
../arch/x86/configs/0xFFA843AA_defconfig obj-x86/.config ; time make
olddefconfig O=obj-x86/ CC=clang-11 fs/ocfs2/journal.i ARCH=x86 -skj30
; wc obj-x86/fs/ocfs2/journal.i
real 0m6.529s
user 0m4.389s
sys 0m2.561s
47377 377887 4178633 obj-x86/fs/ocfs2/journal.i
So both the size of the preprocessed file and the time to preprocess it are
still twice as bad for linux-next compared to mainline. Actually compiling the
preprocessed filed is very quick, as I guess only the preprocessing seems to
use all the time.
Arnd
next prev parent reply other threads:[~2020-05-26 10:42 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-21 14:20 [PATCH -tip v3 00/11] Fix KCSAN for new ONCE (require Clang 11) Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 01/11] ubsan, kcsan: don't combine sanitizer with kcov on clang Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 02/11] kcsan: Avoid inserting __tsan_func_entry/exit if possible Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 03/11] kcsan: Support distinguishing volatile accesses Marco Elver
2020-05-22 10:26 ` Borislav Petkov
2020-05-22 10:34 ` Marco Elver
2020-05-22 10:47 ` Borislav Petkov
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 04/11] kcsan: Pass option tsan-instrument-read-before-write to Clang Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 05/11] kcsan: Remove 'noinline' from __no_kcsan_or_inline Marco Elver
2020-05-29 17:07 ` Peter Zijlstra
2020-05-29 18:36 ` Marco Elver
2020-05-29 18:59 ` Peter Zijlstra
2020-05-21 14:20 ` [PATCH -tip v3 06/11] kcsan: Restrict supported compilers Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 07/11] kcsan: Update Documentation to change " Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 08/11] READ_ONCE, WRITE_ONCE: Remove data_race() and unnecessary checks Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] compiler.h: Remove data_race() and unnecessary checks from {READ,WRITE}_ONCE() tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 09/11] data_race: Avoid nested statement expression Marco Elver
2020-05-21 20:21 ` Nick Desaulniers
2020-05-26 10:42 ` Arnd Bergmann [this message]
2020-05-26 12:02 ` Will Deacon
2020-05-26 12:19 ` Arnd Bergmann
2020-05-26 13:12 ` Marco Elver
2020-05-26 17:33 ` Marco Elver
2020-05-26 19:00 ` Arnd Bergmann
2020-05-26 23:10 ` Arnd Bergmann
2020-05-27 7:22 ` Will Deacon
2020-05-27 7:44 ` Marco Elver
2020-05-27 9:26 ` Arnd Bergmann
2020-05-28 12:53 ` Stephen Rothwell
2020-05-26 21:36 ` Peter Zijlstra
2020-05-21 14:20 ` [PATCH -tip v3 10/11] compiler.h: Move function attributes to compiler_types.h Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 11/11] compiler_types.h, kasan: Use __SANITIZE_ADDRESS__ instead of CONFIG_KASAN to decide inlining Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-22 11:35 ` [PATCH -tip v3 00/11] Fix KCSAN for new ONCE (require Clang 11) 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='CAK8P3a0RJtbVi1JMsfik=jkHCNFv+DJn_FeDg-YLW+ueQW3tNg@mail.gmail.com' \
--to=arnd@arndb.de \
--cc=andreyknvl@google.com \
--cc=bp@alien8.de \
--cc=clang-built-linux@googlegroups.com \
--cc=dvyukov@google.com \
--cc=elver@google.com \
--cc=glider@google.com \
--cc=kasan-dev@googlegroups.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=ndesaulniers@google.com \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=will@kernel.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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).