From: Ingo Molnar <mingo@kernel.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"David S. Miller" <davem@davemloft.net>,
Ard Biesheuvel <ardb@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Al Viro <viro@zeniv.linux.org.uk>,
llvm@lists.linux.dev
Subject: Re: [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell"
Date: Sat, 8 Jan 2022 12:54:26 +0100 [thread overview]
Message-ID: <Ydl7ch/up7qJqByj@gmail.com> (raw)
In-Reply-To: <YdeJgJFRRsIb9pah@archlinux-ax161>
* Nathan Chancellor <nathan@kernel.org> wrote:
> On Tue, Jan 04, 2022 at 11:47:30AM +0100, Ingo Molnar wrote:
> > > > With the fast-headers kernel that's down to ~36,000 lines of code,
> > > > almost a factor of 3 reduction:
> > > >
> > > > # fast-headers-v1:
> > > > kepler:~/mingo.tip.git> wc -l kernel/pid.i
> > > > 35941 kernel/pid.i
> > >
> > > Coming from someone who often has to reduce a preprocessed kernel source
> > > file with creduce/cvise to report compiler bugs, this will be a very
> > > welcomed change, as those tools will have to do less work, and I can get
> > > my reports done faster.
> >
> > That's nice, didn't think of that side effect.
> >
> > Could you perhaps measure this too, to see how much of a benefit it is?
>
> As it turns out, I got an opportunity to measure this sooner rather than
> later [1]. Using cvise [2] with an identical set of toolchains and
> interestingness test [3], reducing net/core/skbuff.c took significantly
> less time with the version from the fast-headers tree.
>
> v5.16-rc8:
>
> $ wc -l skbuff.i
> 105135 skbuff.i
>
> $ time cvise test.fish skbuff.i
> ...
> ________________________________________________________
> Executed in 114.02 mins fish external
> usr time 1180.43 mins 69.29 millis 1180.43 mins
> sys time 229.80 mins 248.11 millis 229.79 mins
>
> fast-headers:
>
> $ wc -l skbuff.i
> 78765 skbuff.i
>
> $ time cvise test.fish skbuff.i
> ...
> ________________________________________________________
> Executed in 47.38 mins fish external
> usr time 620.17 mins 32.78 millis 620.17 mins
> sys time 123.70 mins 122.38 millis 123.70 mins
>
> I was not expecting that much of a difference but it somewhat makes
> sense, as the tool spends less time eliminated unused code and the
> compiler invocations will be incrementally quicker as the input becomes
> smaller.
Indeed, that's a +140% speedup in build performance, not bad. :-)
I also got around testing Clang (12) myself, and with my 'reference distro
config' I got these results:
#
# v5.16-rc8
#
Performance counter stats for 'make -j96 vmlinux LLVM=1' (3 runs):
55,638,543,274,254 instructions # 0.77 insn per cycle ( +- 0.01% )
72,074,911,968,393 cycles # 3.901 GHz ( +- 0.04% )
18,490,451.51 msec cpu-clock # 54.740 CPUs utilized ( +- 0.04% )
337.788 +- 0.834 seconds time elapsed ( +- 0.25% )
#
# -fast-headers-v2-rc3
#
Performance counter stats for 'make -j96 vmlinux LLVM=1' (3 runs):
30,904,130,243,855 instructions # 0.76 insn per cycle ( +- 0.02% )
40,703,482,733,690 cycles # 3.898 GHz ( +- 0.00% )
10,443,670.86 msec cpu-clock # 58.093 CPUs utilized ( +- 0.00% )
179.773 +- 0.829 seconds time elapsed ( +- 0.46% )
That's a +88% build speedup on Clang - even better than the +78% speedup on
GCC(-10).
Thanks,
Ingo
next prev parent reply other threads:[~2022-01-08 11:54 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-02 21:57 [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Ingo Molnar
2022-01-03 10:11 ` Greg Kroah-Hartman
2022-01-03 11:12 ` Ingo Molnar
2022-01-03 13:46 ` Greg Kroah-Hartman
2022-01-03 16:29 ` Ingo Molnar
2022-01-10 10:28 ` Peter Zijlstra
2022-01-04 14:10 ` [PATCH] per_task: Remove the PER_TASK_BYTES hard-coded constant Ingo Molnar
2022-01-04 15:14 ` Andy Shevchenko
2022-01-04 23:27 ` Ingo Molnar
2022-01-04 17:51 ` [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Arnd Bergmann
2022-01-05 0:05 ` Ingo Molnar
2022-01-05 1:37 ` Arnd Bergmann
2022-01-05 9:37 ` Andy Shevchenko
2022-01-04 14:05 ` [PATCH] per_task: Implement single template to define 'struct task_struct_per_task' fields and offsets Ingo Molnar
2022-01-03 13:54 ` [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Kirill A. Shutemov
2022-01-04 10:54 ` Ingo Molnar
2022-01-04 13:34 ` Greg Kroah-Hartman
2022-01-04 13:54 ` [PATCH] headers/uninline: Uninline single-use function: kobject_has_children() Ingo Molnar
2022-01-04 15:09 ` Greg Kroah-Hartman
2022-01-04 15:14 ` Greg Kroah-Hartman
2022-01-05 0:11 ` Ingo Molnar
2022-01-05 15:23 ` Greg Kroah-Hartman
2022-01-06 11:26 ` Ingo Molnar
2022-01-03 17:54 ` [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Nathan Chancellor
2022-01-04 10:47 ` Ingo Molnar
2022-01-04 10:56 ` [DEBUG PATCH] DO NOT MERGE: Enable SHADOW_CALL_STACK on GCC builds, for build testing Ingo Molnar
2022-01-04 11:02 ` [PATCH] headers/deps: dcache: Move the ____cacheline_aligned attribute to the head of the definition Ingo Molnar
2022-01-04 15:05 ` kernel test robot
2022-01-04 17:51 ` Nathan Chancellor
2022-01-05 0:20 ` Ingo Molnar
2022-01-05 0:26 ` [PATCH] headers/deps: Attribute placement fixes for Clang & GCC Ingo Molnar
2022-01-04 11:19 ` [TREE] "Fast Kernel Headers" Tree WIP/development branch Ingo Molnar
2022-01-04 17:25 ` [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Nick Desaulniers
2022-01-05 0:43 ` Ingo Molnar
2022-01-04 17:50 ` Nathan Chancellor
2022-01-05 0:35 ` [PATCH] x86/kbuild: Enable CONFIG_KALLSYMS_ALL=y in the defconfigs Ingo Molnar
2022-01-08 21:57 ` [tip: x86/build] " tip-bot2 for Ingo Molnar
2022-01-05 0:40 ` [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Ingo Molnar
2022-01-05 1:07 ` Ingo Molnar
2022-01-05 5:20 ` [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel'\''s "Dependency Hell Paul Zimmerman
2022-01-05 21:42 ` [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Nathan Chancellor
2022-01-08 10:32 ` [PATCH] headers/deps: Add header dependencies to .c files: <linux/ptrace_api.h> Ingo Molnar
2022-01-08 11:08 ` [PATCH] FIX: headers/deps: uapi/headers: Create usr/include/uapi symbolic link Ingo Molnar
2022-01-08 11:18 ` [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Ingo Molnar
2022-01-08 11:38 ` [PATCH] x86/bitops: Remove unused __sw_hweight64() assembly implementation Ingo Molnar
2022-01-08 11:49 ` [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Ingo Molnar
2022-01-08 12:17 ` Ingo Molnar
2022-01-10 20:03 ` Nathan Chancellor
2022-01-10 20:05 ` Nathan Chancellor
2022-01-05 22:33 ` Nathan Chancellor
2022-01-08 15:16 ` Ingo Molnar
2022-01-07 0:29 ` Nathan Chancellor
2022-01-08 11:54 ` Ingo Molnar [this message]
2022-01-04 12:36 ` Willy Tarreau
2022-01-04 16:05 ` Andy Shevchenko
2022-01-04 16:18 ` Andy Shevchenko
2022-01-15 0:42 ` Paul E. McKenney
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