Re: Proposal: Limitations of palloc inside checkpointer

On Tue, 25 Feb 2025 at 22:44, Ekaterina Sokolova <e(dot)sokolova(at)postgrespro(dot)ru>
wrote:

> Hi, hackers!
>
> Historically, the checkpointer process use palloc() into
> AbsorbSyncRequests() function. Therefore, the checkpointer does not
> expect to receive a request larger than 1 GB.

Yeah. And the most unpleasant thing is it won't simply fail with an error
or helpful message suggesting a workaround (reduce the amount of shared
memory). Checkpointer will just "stuck".

AFAICS, we have a few options:
1. Leave it as it is, but fatal on allocation of the chunk more than 1G.
2. Use palloc_extended with MCXT_ALLOC_HUGE flag.
3. Do not use any allocation and use CheckpointerShmem->requests directly
in case of > 1G size of the required allocation.

Case (3) is not an option, in my opinion. So, we following (1) or (2).
Personally, I'm for (2), PFA v0 patch.

--
Best regards,
Maxim Orlov.