From: Florian Weimer <fweimer@redhat.com>
To: Thomas Fitzsimmons <fitzsim@fitzsim.org>
Cc: Mark Wielaard <mark@klomp.org>,
'GNU C Library' <libc-alpha@sourceware.org>,
Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Subject: Re: [PATCH] Improve performance of IO locks
Date: Tue, 16 Aug 2022 09:31:49 +0200 [thread overview]
Message-ID: <878rnoeja2.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <m3h72c3mzs.fsf@fitzsim.org> (Thomas Fitzsimmons's message of "Mon, 15 Aug 2022 23:07:03 -0400")
* Thomas Fitzsimmons:
> Hi Mark,
>
> Mark Wielaard <mark@klomp.org> writes:
>
>> On Mon, Aug 01, 2022 at 11:06:07AM +0000, Wilco Dijkstra via Libc-alpha wrote:
>>> Improve performance of recursive IO locks by adding a fast path for
>>> the single-threaded case. To reduce the number of memory accesses for
>>> locking/unlocking, only increment the recursion counter if the lock
>>> is already taken.
>>>
>>> On Neoverse V1, a microbenchmark with many small freads improved by
>>> 2.9 times. Multithreaded performance improved by 2%.
>>
>> Strangely this seems to have broken the glibc-debian-ppc64 buildbot:
>> https://builder.sourceware.org/buildbot/#/builders/glibc-debian-ppc64
>>
>> I don't see how this commit can cause a failure just on debian-ppc64
>> (all other distro/arches are fine).
>>
>> And the corresponding bunsen test results don't really show why.
>> https://builder.sourceware.org/testrun/498f51f327afdd7030516455b709a31a0038b432
>> Most of the .out files are empty, but some indicate an segmentation fault.
>>
>> Comparing to the build before only shows test result diffs, no
>> configuration differences.
>> https://builder.sourceware.org/testrun-diffs?commitish=498f51f327afdd7030516455b709a31a0038b432&commitish=58fd9d63b078b6bbfdba45135c4021038f33534e
>>
>> I don't have access to the buildbot, so cannot easily investigate more.
>>
>> Tom, could you have a look and see if you can find out more? Does just
>> reverting commit c51c483d2b8ae66fe31a12509aedae02a6982ced make things
>> OK again?
>
> Yes reverting that commit, the result is:
>
> Summary of test results:
> 317 PASS
> 10 UNSUPPORTED
> 2 XPASS
>
> Without the reversion:
>
> Summary of test results:
> 256 FAIL
> 68 PASS
> 3 UNSUPPORTED
> 2 XFAIL
>
> I looked at elf/unload as an example; it's segfaulting in
> _dl_relocate_object, backtrace attached; not sure what else to check.
I don't see this on powerpc64, with a toolchain based on GCC 8.2 and
binutils 2.30. I'm at a loss how these things could be related.
Thanks,
Florian
next prev parent reply other threads:[~2022-08-16 7:31 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-08 16:32 Wilco Dijkstra
2022-08-01 11:06 ` Wilco Dijkstra
2022-08-07 12:51 ` Cristian Rodríguez
2022-08-15 22:27 ` Mark Wielaard
2022-08-16 3:07 ` Thomas Fitzsimmons
2022-08-16 7:31 ` Florian Weimer [this message]
2022-08-16 10:00 ` Mark Wielaard
2022-08-16 10:08 ` Florian Weimer
2022-08-17 13:45 ` Mark Wielaard
2022-08-22 10:25 ` Florian Weimer
2022-08-22 14:58 ` Frank Ch. Eigler
2022-08-16 11:19 ` Andreas Schwab
2022-08-16 10:24 ` Wilco Dijkstra
2022-08-16 13:18 ` Thomas Fitzsimmons
2022-08-16 14:31 ` Thomas Fitzsimmons
2022-08-17 11:53 ` Mark Wielaard
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