Re: stats collector suddenly causing lots of IO

On Fri, Apr 16, 2010 at 11:41 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Wow.  Well, we have a smoking gun here: for some reason, autovacuum
> isn't running, or isn't doing its job if it is.  If it's not running
> at all, that would explain failure to prune the stats collector's file
> too.

Hrm, well autovacuum is at least trying to do work: it's currently
stuck on those bloated pg_catalog tables, of course. Another developer
killed an autovacuum of pg_attribute (or maybe it was pg_attrdef)
after it had been running for two weeks. See current pg_stat_activity
output attached, which shows the three autovacuum workers running plus
two manual VACUUM ANALYZEs I started yesterday.

> Is there anything in the postmaster log that would suggest autovac
> difficulties?

Yup, there are logs from April 1st which I just grepped through. I
attached the redacted output, and I see a few warnings about "[table]
contains more than "max_fsm_pages" pages with useful free space", as
well as "ERROR: canceling autovacuum task".

Perhaps bumping up max_fsm_pages and making autovacuum settings more
aggressive will help me? I was also planning to run a CLUSTER of those
four bloated pg_catalog tables -- is this safe, particularly for
tables like pg_attrdef which rely on OIDs?

Josh