Re: Background writer and checkpointer in crash recovery

On Wed, Nov 11, 2020 at 9:57 PM Simon Riggs <simon@2ndquadrant.com> wrote:
> Having said that, we did raise the checkpoint_timeout by a lot, so the
> situation today might be quite different. A large checkpoint_timeout
> could eventually overflow shared buffers, with the right workload.

FWIW Jakuk Wartak did manage to show a 1.64x speedup while running
crash recovery of an insert-only workload (with a variant of this
patch that I shared in another thread), albeit with aggressive tuning:


https://www.postgresql.org/message-id/VI1PR0701MB6960EEB838D53886D8A180E3F6520%40VI1PR0701MB6960.eurprd07.prod.outlook.com

> We don't have any stats to show whether this patch is worthwhile or
> not, so I suggest adding the attached instrumentation patch as well so
> we can see on production systems whether checkpoint_timeout is too
> high by comparison with pg_stat_bgwriter. The patch is written in the
> style of log_checkpoints.

Very useful.  I've also been wondering how to get that sort of
information in hot standby.