On Fri, May 13, 2016 at 11:13 PM, Andres Freund <andres@anarazel.de> wrote: > > On 2016-05-13 10:20:04 -0400, Robert Haas wrote: > > On Fri, May 13, 2016 at 7:08 AM, Ashutosh Sharma <ashu.coek88@gmail.com> wrote: > > > Following are the performance results for read write test observed with > > > different numbers of "backend_flush_after". > > > > > > 1) backend_flush_after = 256kb (32*8kb), tps = 10841.178815 > > > 2) backend_flush_after = 512kb (64*8kb), tps = 11098.702707 > > > 3) backend_flush_after = 1MB (128*8kb), tps = 11434.964545 > > > 4) backend_flush_after = 2MB (256*8kb), tps = 13477.089417 > > > > So even at 2MB we don't come close to recovering all of the lost > > performance. Can you please test these three scenarios? > > > > 1. Default settings for *_flush_after > > 2. backend_flush_after=0, rest defaults > > 3. backend_flush_after=0, bgwriter_flush_after=0, > > wal_writer_flush_after=0, checkpoint_flush_after=0 > > 4) 1) + a shared_buffers setting appropriate to the workload. >
If by 4th point, you mean to test the case when data fits in shared buffers, then Mithun has already reported above [1] that it didn't see any regression for that case