From: | "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, tender wang <tndrwang(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock |
Date: | 2023-12-18 17:53:43 |
Message-ID: | 532DE4E9-F02A-4984-A0D0-A6CBA82B60A8@yandex-team.ru |
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Lists: | pgsql-hackers |
> On 18 Dec 2023, at 22:30, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Mon, Dec 18, 2023 at 12:04 PM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> certain sense they are competing for the same job. However, they do
>> aim to alleviate different TYPES of contention: the group XID update
>> stuff should be most valuable when lots of processes are trying to
>> update the same page, and the banks should be most valuable when there
>> is simultaneous access to a bunch of different pages. So I'm not
>> convinced that this patch is a reason to remove the group XID update
>> mechanism, but someone might argue otherwise.
>
> Hmm, but, on the other hand:
>
> Currently all readers and writers are competing for the same LWLock.
> But with this change, the readers will (mostly) no longer be competing
> with the writers. So, in theory, that might reduce lock contention
> enough to make the group update mechanism pointless.
One page still accommodates 32K transaction statuses under one lock. It feels like a lot. About 1 second of transactions on a typical installation.
When the group commit was committed did we have a benchmark to estimate efficiency of this technology? Can we repeat that test again?
Best regards, Andrey Borodin.
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