Re: Perf Benchmarking and regression.

On Fri, May 13, 2016 at 11:13 PM, Andres Freund <andres(at)anarazel(dot)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(dot)coek88(at)gmail(dot)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

[1] -
http://www.postgresql.org/message-id/CAD__OuiObzNVTt_hO__P5AEnU4iNqcFWgArXR4TbLKe-UXyukQ@mail.gmail.com
Read line - Even for READ-WRITE when data fits into shared buffer
(scale_factor=300 and shared_buffers=8GB) performance has improved.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com