Re: Excessive PostmasterIsAlive calls slow down WAL redo

Hi,

On 2018-04-06 07:39:28 -0400, Stephen Frost wrote:
> While I tend to agree that it'd be nice to just make it cheaper, that
> doesn't seem like something that we'd be likely to back-patch and I tend
> to share Heikki's feelings that this is a performance regression we
> should be considering fixing in released versions.

I'm doubtful about fairly characterizing this as a performance bug. It's
not like we've O(n^2) behaviour on our hand, and if your replay isn't of
a toy workload normally that one syscall isn't going to make a huge
difference because you've actual IO and such going on.

I'm also doubtful that it's sane to just check every 32 records. There's
records that can take a good chunk of time, and just continuing for
another 31 records seems like a bad idea.

Greetings,

Andres Freund