| From: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
|---|---|
| To: | Michail Nikolaev <michail(dot)nikolaev(at)gmail(dot)com> |
| Cc: | Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, Andres Freund <andres(at)anarazel(dot)de>, Kirill Reshke <reshkekirill(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Slow standby snapshot |
| Date: | 2021-11-16 02:00:08 |
| Message-ID: | CAPpHfdvwceRC3YrATakUdYqvJLiFf1tOwvvo6-Dpq==AHwvQkg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Nov 10, 2021 at 12:16 AM Michail Nikolaev
<michail(dot)nikolaev(at)gmail(dot)com> wrote:
> I updated the patch a little. KnownAssignedXidsGetAndSetXmin now
> causes fewer cache misses because some values are stored in variables
> (registers). I think it is better to not lean on the compiler here
> because of `volatile` args.
> Also, I have added some comments.
It looks like KnownAssignedXidsNext doesn't have to be
pg_atomic_uint32. I see it only gets read with pg_atomic_read_u32()
and written with pg_atomic_write_u32(). Existing code believes that
read/write of 32-bit values is atomic. So, you can use just uint32
instead of pg_atomic_uint32.
------
Regards,
Alexander Korotkov
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