Re: pg_stat_bgwriter

I find the background writer to be pretty unimportant these days.  If the kernel is freely accepting writes without blocking, the backends can probably write their own buffers without it being a meaningful bottleneck.  On the other hand, if the kernel is constipated, no tweaking of the background writer parameters is going to insulate the backends from that fact.  That said, I would increase bgwriter_lru_maxpages (or decrease bgwriter_delay) anyway.  It probably won't make much difference, but if it does it is more likely to help than to hurt.

 

I don't think that that comparison is meaningful, so wouldn't make changes based on it.

 

If you are experiencing a problem, this is probably not the right way to investigate it.  If a particular query is slow, try EXPLAIN (ANALYZE, BUFFERS).  If lots of user-facing things are slow, try sampling "select wait_event, wait_event_type  from pg_stat_activity where backend_type='client backend';"