From: | "lingce(dot)ldm" <lingce(dot)ldm(at)alibaba-inc(dot)com> |
---|---|
To: | Michael Paquier <michael(at)paquier(dot)xyz> |
Cc: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, masao(dot)fujii(at)gmail(dot)com, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Problem with synchronous replication |
Date: | 2019-11-01 05:27:54 |
Message-ID: | 806F744F-F568-4B5F-B8F3-13077BA23721@alibaba-inc.com |
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Lists: | pgsql-hackers |
On Oct 31, 2019, at 10:11, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> On Wed, Oct 30, 2019 at 05:43:04PM +0900, Kyotaro Horiguchi wrote:
>> At Wed, 30 Oct 2019 17:21:17 +0900, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote in
>>> This change causes every ending backends to always take the exclusive lock
>>> even when it's not in SyncRep queue. This may be problematic, for example,
>>> when terminating multiple backends at the same time? If yes,
>>> it might be better to check SHMQueueIsDetached() again after taking the lock.
>>> That is,
>>
>> I'm not sure how much that harms but double-checked locking
>> (releasing) is simple enough for reducing possible congestion here, I
>> think.
>
> FWIW, I could not measure any actual difference with pgbench -C, up to
> 500 sessions and an empty input file (just have one meta-command) and
> -c 20.
>
> I have added some comments in SyncRepCleanupAtProcExit(), and adjusted
> the patch with the suggestion from Fujii-san. Any comments?
Thanks for the patch. Looks good to me +1.
Regards,
—
Dongming Liu
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