Re: 8.2 is 30% better in pgbench than 8.3

2007/7/21, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> "Pavel Stehule" <pavel(dot)stehule(at)gmail(dot)com> writes:
> > I was little bit surprised. Is any reason for it?
>
> Are you sure you're comparing apples to apples? In particular the
> default autovacuuming setup is entirely different. With autovac off
> I see 8.3 as faster than 8.2 in pgbench.

I am not sure. But this (or similar) test will do more persons, and
the difference have to be explained.

>
> Also, remember a couple rules of thumb for choosing pgbench parameters:
> keep -c less than the -s scale factor you used for pgbench -i (otherwise
> you're mostly measuring update contention, because there are only -s
> different rows in the branches table); and use -t at least 1000 or so
> (otherwise startup transients are significant).

Ok, I have to do more tests.

>
> Note to all: we ***HAVE TO*** settle on some reasonable default
> vacuum_cost_delay settings before we can ship 8.3. With no cost delay
> and two or three workers active, 8.3's autovac does indeed send
> performance into the tank.
>

Thank you for reply

Pavel Stehule