Re: How to interpret view pg_stat_bgwriter

On 9/16/14 2:42 AM, Huang, Suya wrote:
> # checkpoints_req is much bigger than checkpoints_timed, suggest that I
> may increase checkpoint_segments in our system

That's not strictly necessary, but personally I think both of those
settings are too low for you.

> #maxwritten_clean is high, suggests increase bgwriter_lru_maxpages

Yes.

> # buffers_backend is much smaller than buffers_alloc, suggests
> increasing bgwriter_lru_maxpages, bgwriter_lru_multiplier, and
> decreasing bgwriter_delay.

You should rather compare buffers_backend against buffers_checkpoint.

Also consider graphing these quantities over time so you can see how
different workloads affects the results and what the effects of your
tuning are.

Also turn on log_checkpoints and look at the sync times. In my
experience that dominates all the bgwriter tuning.