Re: pgstat wait timeout (RE: contrib/cache_scan)

Kouhei Kaigai <kaigai@ak.jp.nec.com> writes:
> WARNING:  pgstat wait timeout
> WARNING:  pgstat wait timeout
> WARNING:  pgstat wait timeout
> WARNING:  pgstat wait timeout

> Once I got above messages, write performance is dramatically
> degraded, even though I didn't take detailed investigation.

> I could reproduce it on the latest master branch without my
> enhancement, so I guess it is not a problem something special
> to me.
> One other strangeness is, right now, this problem is only
> happen on my virtual machine environment - VMware ESXi 5.5.0.
> I couldn't reproduce the problem on my physical environment
> (Fedora20, core i5-4570S).

We've seen sporadic reports of that sort of behavior for years, but no
developer has ever been able to reproduce it reliably.  Now that you've
got a reproducible case, do you want to poke into it and see what's going
on?
        regards, tom lane