From: Nadav Amit <namit@vmware.com>
To: "hpa@zytor.com" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Jan Beulich <JBeulich@suse.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH v9 04/10] x86: refcount: prevent gcc distortions
Date: Thu, 4 Oct 2018 08:56:37 +0000 [thread overview]
Message-ID: <A5DED74C-A95A-48D8-AF68-39E23696385F@vmware.com> (raw)
In-Reply-To: <10D29A50-C352-4407-A824-0C3C06CD8592@zytor.com>
at 1:40 AM, hpa@zytor.com wrote:
> On October 4, 2018 1:33:33 AM PDT, Ingo Molnar <mingo@kernel.org> wrote:
>> * Ingo Molnar <mingo@kernel.org> wrote:
>>
>>> I'm also somewhat annoyed at the fact that this series carries a
>> boatload
>>> of reviewed-by's and acked-by's, yet none of those reviewers found it
>>> important to point out the large chasm that is gaping between
>> description
>>> and reality.
>>
>> Another problem I just realized is that we now include
>> arch/x86/kernel/macros.S in every
>> translation pass when building the kernel, right?
>>
>> But arch/x86/kernel/macros.S expands to a pretty large hiearchy of
>> header files:
>>
>> $ make arch/x86/kernel/macros.s
>>
>> $ cat $(grep include arch/x86/kernel/macros.s | cut -d\" -f2 | sort |
>> uniq) | wc -l
>> 4128
>>
>> That's 4,100 extra lines of code to be preprocessed for every
>> translation unit, of
>> which there are tens of thousands. More if other pieces of code get
>> macrofied in
>> this fasion in the future.
>>
>> If we assume that a typical distribution kernel build has ~20,000
>> translation units
>> then this change adds 82,560,000 more lines to be preprocessed, just to
>> work around
>> a stupid GCC bug?
>>
>> I'm totally unhappy about that. Can we do this without adding macros.S?
>>
>> It's also a pretty stupidly central file anyway that moves source code
>> away
>> from where it's used.
>>
>> Thanks,
>>
>> Ingo
>
> It's not just for working around a stupid GCC bug, but it also has a huge
> potential for cleaning up the inline asm in general.
>
> I would like to know if there is an actual number for the build overhead
> (an actual benchmark); I have asked for that once already.
I can run some tests. (@hpa: I thought you asked about the -pipe overhead;
perhaps I misunderstood).
I guess you regard to the preprocessing of the assembler. Note that the C
preprocessing of macros.S obviously happens only once. That’s the reason
I assumed it’s not that expensive.
Anyhow, I remember that we discussed at some point doing something like
‘asm(“.include XXX.s”)’ and somebody said it is not good, but I don’t
remember why and don’t see any reason it is so. Unless I am missing
something, I think it is possible to take each individual header and
preprocess the assembly part of into a separate .s file. Then we can put in
the C part of the header ‘asm(".include XXX.s”)’.
What do you think?
next prev parent reply other threads:[~2018-10-04 8:56 UTC|newest]
Thread overview: 116+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-03 21:30 [PATCH v9 00/10] x86: macrofying inline asm Nadav Amit
2018-10-03 21:30 ` [PATCH v9 01/10] xtensa: defining LINKER_SCRIPT for the linker script Nadav Amit
2018-10-04 10:00 ` [tip:x86/build] kbuild/arch/xtensa: Define " tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 02/10] Makefile: Prepare for using macros for inline asm Nadav Amit
2018-10-04 10:01 ` [tip:x86/build] kbuild/Makefile: Prepare for using macros in inline assembly code to work around asm() related GCC inlining bugs tip-bot for Nadav Amit
2018-11-06 18:57 ` [PATCH v9 02/10] Makefile: Prepare for using macros for inline asm Logan Gunthorpe
2018-11-06 19:18 ` Nadav Amit
2018-11-06 20:01 ` Logan Gunthorpe
2018-11-07 18:01 ` Nadav Amit
2018-11-07 18:53 ` Logan Gunthorpe
2018-11-07 18:56 ` Nadav Amit
2018-11-07 21:43 ` Logan Gunthorpe
2018-11-07 21:50 ` hpa
2018-11-08 6:18 ` Nadav Amit
2018-11-08 17:14 ` Logan Gunthorpe
2018-11-08 19:54 ` Nadav Amit
2018-11-08 20:00 ` Logan Gunthorpe
2018-11-08 20:18 ` Nadav Amit
2018-11-10 22:04 ` Nadav Amit
2018-11-13 4:56 ` Logan Gunthorpe
2018-10-03 21:30 ` [PATCH v9 03/10] x86: objtool: use asm macro for better compiler decisions Nadav Amit
2018-10-04 10:02 ` [tip:x86/build] x86/objtool: Use asm macros to work around GCC inlining bugs tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 04/10] x86: refcount: prevent gcc distortions Nadav Amit
2018-10-04 7:57 ` Ingo Molnar
2018-10-04 8:33 ` Ingo Molnar
2018-10-04 8:40 ` hpa
2018-10-04 8:56 ` Ingo Molnar
2018-10-04 8:56 ` Nadav Amit [this message]
2018-10-04 9:02 ` hpa
2018-10-04 9:16 ` Ingo Molnar
2018-10-04 19:33 ` H. Peter Anvin
2018-10-04 20:05 ` Nadav Amit
2018-10-04 20:08 ` H. Peter Anvin
2018-10-04 20:29 ` Andy Lutomirski
2018-10-04 23:11 ` H. Peter Anvin
2018-10-06 1:40 ` Rasmus Villemoes
2018-10-04 9:12 ` Ingo Molnar
2018-10-04 9:17 ` hpa
2018-10-04 9:30 ` Nadav Amit
2018-10-04 9:45 ` Ingo Molnar
2018-10-04 10:23 ` Nadav Amit
2018-10-05 9:31 ` Ingo Molnar
2018-10-05 11:20 ` Borislav Petkov
2018-10-05 12:52 ` Ingo Molnar
2018-10-05 20:27 ` [PATCH 0/3] Macrofying inline asm rebased Nadav Amit
2018-10-05 20:27 ` [PATCH 1/3] x86/extable: Macrofy inline assembly code to work around GCC inlining bugs Nadav Amit
2018-10-06 14:42 ` [tip:x86/build] " tip-bot for Nadav Amit
2018-10-05 20:27 ` [PATCH 2/3] x86/cpufeature: " Nadav Amit
2018-10-06 14:43 ` [tip:x86/build] " tip-bot for Nadav Amit
2018-10-05 20:27 ` [PATCH 3/3] x86/jump-labels: " Nadav Amit
2018-10-06 14:44 ` [tip:x86/build] " tip-bot for Nadav Amit
2018-10-08 2:17 ` [PATCH v9 04/10] x86: refcount: prevent gcc distortions Nadav Amit
2018-10-04 8:40 ` Nadav Amit
2018-10-04 9:01 ` Ingo Molnar
2018-10-04 10:02 ` [tip:x86/build] x86/refcount: Work around GCC inlining bug tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 05/10] x86: alternatives: macrofy locks for better inlining Nadav Amit
2018-10-04 10:03 ` [tip:x86/build] x86/alternatives: Macrofy lock prefixes to work around GCC inlining bugs tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 06/10] x86: bug: prevent gcc distortions Nadav Amit
2018-10-04 10:03 ` [tip:x86/build] x86/bug: Macrofy the BUG table section handling, to work around GCC inlining bugs tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 07/10] x86: prevent inline distortion by paravirt ops Nadav Amit
2018-10-04 10:04 ` [tip:x86/build] x86/paravirt: Work around GCC inlining bugs when compiling " tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 08/10] x86: extable: use macros instead of inline assembly Nadav Amit
2018-10-03 21:30 ` [PATCH v9 09/10] x86: cpufeature: " Nadav Amit
2018-10-03 21:31 ` [PATCH v9 10/10] x86: jump-labels: " Nadav Amit
2018-10-07 9:18 ` PROPOSAL: Extend inline asm syntax with size spec Borislav Petkov
[not found] ` <20181007132228.GJ29268@gate.crashing.org>
2018-10-07 14:13 ` Borislav Petkov
2018-10-07 15:14 ` Segher Boessenkool
2018-10-08 5:58 ` Ingo Molnar
2018-10-08 7:53 ` Segher Boessenkool
2018-10-07 15:53 ` Michael Matz
2018-10-08 6:13 ` Ingo Molnar
2018-10-08 8:18 ` Segher Boessenkool
2018-10-08 7:31 ` Segher Boessenkool
2018-10-08 9:07 ` Richard Biener
2018-10-08 10:02 ` Segher Boessenkool
2018-10-09 14:53 ` Segher Boessenkool
2018-10-10 6:35 ` Ingo Molnar
2018-10-10 7:12 ` Richard Biener
2018-10-10 7:22 ` Ingo Molnar
2018-10-10 8:03 ` Segher Boessenkool
2018-10-10 8:19 ` Borislav Petkov
2018-10-10 8:35 ` Richard Biener
2018-10-10 18:54 ` Segher Boessenkool
2018-10-10 19:14 ` Borislav Petkov
2018-10-13 19:33 ` Borislav Petkov
2018-10-13 21:14 ` Alexander Monakov
2018-10-13 21:30 ` Borislav Petkov
2018-10-25 10:24 ` Borislav Petkov
2018-10-31 12:55 ` Peter Zijlstra
2018-10-31 13:11 ` Peter Zijlstra
2018-10-31 16:31 ` Segher Boessenkool
2018-11-01 5:20 ` Joe Perches
2018-11-01 9:01 ` Peter Zijlstra
2018-11-01 9:20 ` Joe Perches
2018-11-01 11:15 ` Peter Zijlstra
2018-12-27 4:47 ` Masahiro Yamada
2018-10-10 10:29 ` Richard Biener
2018-10-10 7:53 ` Segher Boessenkool
2018-10-10 16:31 ` Nadav Amit
2018-10-10 19:21 ` Segher Boessenkool
2018-10-11 7:04 ` Richard Biener
2018-11-29 11:46 ` Masahiro Yamada
2018-11-29 12:25 ` Segher Boessenkool
2018-11-30 9:06 ` Boris Petkov
2018-11-30 13:16 ` Segher Boessenkool
2018-12-10 8:16 ` Masahiro Yamada
2018-11-29 13:07 ` Borislav Petkov
2018-11-29 13:09 ` Richard Biener
2018-11-29 13:16 ` Borislav Petkov
2018-11-29 13:24 ` Richard Biener
2018-10-08 16:24 ` David Laight
2018-10-07 16:09 ` Nadav Amit
2018-10-07 16:46 ` Richard Biener
2018-10-07 19:06 ` Nadav Amit
2018-10-07 19:52 ` Jeff Law
2018-10-08 7:46 ` Richard Biener
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