| From: | Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru>, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
| Subject: | Re: Fix bank selection logic in SLRU |
| Date: | 2024-12-10 14:05:42 |
| Message-ID: | CAFiTN-u9Ba8Wve6ed2n80cnmVYWGM=yirM03F5t0e5gSrHgEYg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, 10 Dec 2024 at 7:30 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Tue, Dec 10, 2024 at 8:58 AM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> >> Bank selection code assumes that number of buffers is power of 2.
> >> If the number of buffers is not power of 2 - only subset of buffers
> will be used. In worst case, e.g. 65 buffers, everything will be buffered
> only in bank 64.
> >
> > But why that would be the case? the acceptable values for GUC to
> configure the slru buffers are in multiple of 16(bank size) we have that
> check to check the GUC values.
>
> "Must be a multiple of 16" and "must be a power of 2" are different
> criteria. For example, 48 is a multiple of 16 but it is not a power of
> 2. If the code assumes that we have an actual power of 2, the check
> you quoted in your previous email is insufficient.
Yeah I see it’s an issue. Thanks for clarifying.
—
Dilip
>
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