| From: | "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
| Cc: | Dilip Kumar <dilipbalaut(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: | 2023-11-06 11:14:32 |
| Message-ID: | 01204A45-D792-4EAD-8963-F13B47972B87@yandex-team.ru |
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| Lists: | pgsql-hackers |
> On 6 Nov 2023, at 14:31, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
>
> dynahash is notoriously slow, which is why we have simplehash.h since
> commit b30d3ea824c5. Maybe we could use that instead.
Dynahash has lock partitioning. Simplehash has not, AFAIK.
The thing is we do not really need a hash function - pageno is already a best hash function itself. And we do not need to cope with collisions much - we can evict a collided buffer.
Given this we do not need a hashtable at all. That’s exact reasoning how banks emerged, I started implementing dynahsh patch in April 2021 and found out that “banks” approach is cleaner. However the term “bank” is not common in software, it’s taken from hardware cache.
Best regards, Andrey Borodin.
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