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Re: [PATCH v2] rwlock: Fix explicit hand-over.
- From: Waiman Long <longman at redhat dot com>
- To: Torvald Riegel <triegel at redhat dot com>, Florian Weimer <fw at deneb dot enyo dot de>
- Cc: GLIBC Devel <libc-alpha at sourceware dot org>, Carlos O'Donell <codonell at redhat dot com>
- Date: Mon, 27 Mar 2017 12:09:41 -0400
- Subject: Re: [PATCH v2] rwlock: Fix explicit hand-over.
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On 03/25/2017 07:01 PM, Torvald Riegel wrote:
> On Sat, 2017-03-25 at 21:17 +0100, Florian Weimer wrote:
>> * Torvald Riegel:
>>
>>> + bool registered_while_in_write_phase = false;
>>> if (__glibc_likely ((r & PTHREAD_RWLOCK_WRPHASE) == 0))
>>> return 0;
>>> + else
>>> + registered_while_in_write_phase = true;
>> Sorry, this doesn't look quite right. Isn't
>> registered_while_in_write_phase always true?
> Attached is a v2 patch. It's the same logic, but bigger. Most of this
> increase is due to reformatting, but I also adapted some of the
> comments.
> I get two failures, but I guess these are either due to the bad internet
> connectivity I currently have, or something at the resolver.
> FAIL: resolv/mtrace-tst-leaks
> FAIL: resolv/tst-leaks
>
>
I have verified that the v2 patch did fix the hang that I saw with my
microbenchmark. I also observed an increase in performance in the new
rwlock code compared with the old one before the major rewrite. On a
4-socket 40-core 80-thread system, 80 parallel locking threads had an
average per-thread throughput of 32,584 ops/s. The old rwlock code had a
throughput of 13,411 only. So there is a more than 1.4X increase in
performance.
Tested-by: Waiman Long <longman@redhat.com>
Cheers,
Longman