Re: checkpointer continuous flushing - V16

On 2016-03-07 09:41:51 -0800, Andres Freund wrote:
> > Due to the difference in amount of RAM, each machine used different scales -
> > the goal is to have small, ~50% RAM, >200% RAM sizes:
> > 
> > 1) Xeon: 100, 400, 6000
> > 2) i5: 50, 200, 3000
> > 
> > The commits actually tested are
> > 
> >    cfafd8be  (right before the first patch)
> >    7975c5e0  Allow the WAL writer to flush WAL at a reduced rate.
> >    db76b1ef  Allow SetHintBits() to succeed if the buffer's LSN ...
> 
> Huh, now I'm a bit confused. These are the commits you tested? Those
> aren't the ones doing sorting and flushing?

To clarify: The reason we'd not expect to see much difference here is
that the above commits really only have any affect above noise if you
use synchronous_commit=off. Without async commit it's just one
additional gettimeofday() call and a few additional branches in the wal
writer every wal_writer_delay.

Andres