Re: postgresql latency & bgwriter not doing its job

Hello again,

>> I have not found any mean to force bgwriter to send writes when it can.
>> (Well, I have: create a process which sends "CHECKPOINT" every 0.2
>> seconds... it works more or less, but this is not my point:-)
>
> There is scan_whole_pool_milliseconds, which currently forces bgwriter to
> circle the buffer pool at least once every 2 minutes.  It is currently
> fixed, but it should be trivial to turn it into an experimental guc that
> you could use to test your hypothesis.

I recompiled with the variable coldly set to 1000 instead of 120000. The 
situation is slightly degraded (15% of transactions were above 200 ms 
late). However it seems that bgwriter did not write much more pages:
  buffers_checkpoint = 26065  buffers_clean = 5263  buffers_backend = 367

Or I may have a problem interpreting pg_stat_bgwriter.

It seems that changing this value is not enough to persuade bgwriter to 
write more pages. Or I may have done something wrong, but I do not know 
what.

-- 
Fabien.