Re: 8.0.X and the ARC patent - Mailing list pgsql-hackers

Michael Adler <adler@pobox.com> writes:
> Looking at the "Response Time Charts" 

> 8.0.1/ARC
> http://www.osdl.org/projects/dbt2dev/results/dev4-010/309/rt.html

> 20050301 with 2Q patch
> http://www.osdl.org/projects/dbt2dev/results/dev4-010/313/rt.html

> It seems like the average response time has gone down, but the worse
> case ceiling has raised about 35%.

The worst cases are associated with checkpoints.  I'm not sure why a
checkpoint would have a greater effect on the 2Q system than an ARC
system --- checkpoint doesn't request any new buffers so you'd think
it'd be independent.  Maybe this says that the bgwriter is less
effective with 2Q, so that there are more dirty buffers remaining to
be written at the checkpoint?  But why?
        regards, tom lane