From: Waiman Long <longman@redhat.com>
To: Torvald Riegel <triegel@redhat.com>
Cc: Florian Weimer <fw@deneb.enyo.de>,
GLIBC Devel <libc-alpha@sourceware.org>,
Carlos O'Donell <codonell@redhat.com>
Subject: Re: [PATCH v2] rwlock: Fix explicit hand-over.
Date: Mon, 27 Mar 2017 18:59:00 -0000 [thread overview]
Message-ID: <58a61371-e31e-055a-d561-c0e1c13eb7c1@redhat.com> (raw)
In-Reply-To: <9be4ac93-b326-ad21-b190-5fd4e897dabd@redhat.com>
On 03/27/2017 02:16 PM, Waiman Long wrote:
> On 03/27/2017 01:53 PM, Torvald Riegel wrote:
>> On Mon, 2017-03-27 at 12:09 -0400, Waiman Long wrote:
>>> 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.
>> Thanks!
>>
>>> 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.
>> Is that with the 50% reads / 50% writes workload (per thread), empty
>> critical sections, and no delay between critical sections?
>>
> Yes, I used the default configuration of 1:1 read/write ratio. The
> critical section isn't exactly empty as I used 1 pause instruction for
> both in the critical section and between critical section.
>
> Regards,
> Longman
>
Just found out that there is a regression in performance when in writer
preferring mode. The average per-thread throughput was 4,733 ops/s with
the old glibc, but 2,300 ops/s with the new implementation vs 32,584
ops/s for the reader-preferring mode. It was said in the code that
writer-preferring mode isn't the focus in the rewrite. So I am not
saying that it is bad, but it is something to keep in mind about.
Regards,
Longman
next prev parent reply other threads:[~2017-03-27 18:59 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-25 19:50 [PATCH] " Torvald Riegel
2017-03-25 20:17 ` Florian Weimer
2017-03-25 20:39 ` Torvald Riegel
2017-03-25 23:01 ` [PATCH v2] " Torvald Riegel
2017-03-27 16:09 ` Waiman Long
2017-03-27 17:54 ` Torvald Riegel
2017-03-27 18:16 ` Waiman Long
2017-03-27 18:59 ` Waiman Long [this message]
2017-03-27 19:11 ` Waiman Long
2017-04-06 10:51 ` Torvald Riegel
2017-04-06 10:47 ` Torvald Riegel
2017-04-06 10:51 ` Ping! " Torvald Riegel
2017-07-28 5:41 ` Carlos O'Donell
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