Re: Make ringbuffer threshold and ringbuffer sizes configurable?

On Wed, 2020-02-05 at 20:00 -0800, Andres Freund wrote:
> The ringbuffers we use for seqscans, vacuum, copy etc can cause very
> drastic slowdowns (see e.g. [1]), an can cause some workloads to
> practically never end up utilizing shared buffers. ETL workloads
> e.g. regularly fight with that problem.
>
> I think it would make sense to have seqscan_ringbuffer_threshold,
> {bulkread,bulkwrite,vacuum}_ringbuffer_size. I think they often sensibly
> are set in proportion of shared_buffers, so I suggest defining them as
> floats, where negative values divide shared_buffers, whereas positive
> values are absolute sizes, and 0 disables the use of ringbuffers.

Sounds reasonable.

I feel that it should be as few GUCs as possible, so I think that
having one per type of operation might be too granular.

This should of course also be a storage parameter that can be
set per table.

Yours,
Laurenz Albe