On 2018-04-30 16:07:48 -0700, Peter Geoghegan wrote:
> On Mon, Apr 30, 2018 at 4:03 PM, Andres Freund <andres@anarazel.de> wrote:
> >> Is this a problem in practice, though? I don't remember seeing any reports
> >> of the fsync queue filling up, after we got the code to compact it. I don't
> >> know if anyone has been looking for that, so that might also explain the
> >> absence of reports, though.
> >
> > It's probably hard to diagnose that as the origin of slow IO from the
> > outside. It's not exactly easy to diagnose that even if you know what's
> > going on.
>
> True, but has anyone ever actually observed a non-zero
> pg_stat_bgwriter.buffers_backend_fsync in the wild after the
> compaction queue stuff was added/backpatched?
Yes.
Greetings,
Andres Freund