On Tue, Sep 2, 2014 at 8:14 AM, Fabien COELHO <coe...@cri.ensmp.fr> wrote:
> > 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: >>> >> >> >> You should probably try it set to 200 rather than 1000, to put it on an >> equal footing with the checkpoint_timeout of 0.2 seconds you reported on. >> > > As I understand it, the setting makes the bgwriter processe scan all > shared_buffers every this amount of time... but ITSM that the key point is > that bgwriter has no insentive to start writing out buffers anyway with its > current decision rules, and that should not change with the frequency at > which they are scanned (?) Ah, I see now. The usage counts are not zero, so it visits the buffer and then leaves it alone. Cheers, Jeff
