Re: effective cache size on FreeBSD (WAS: Performance on SUSE w/

> > > Apparently this formula is no longer relevant on the FreeBSD systems as
> > > it can cache up to almost all the available RAM. With 4GB of RAM, one
> > > could specify most of the RAM as being available for caching, assuming
> > > that nothing but PostgreSQL runs on the server -- certainly 1/2 the RAM
> > > would be a reasonable value to tell the planner.
> > >
> > > (This was verified by using dd:
> > > dd if=/dev/zero of=/usr/local/pgsql/iotest bs=128k count=16384 to create
> > > a 2G file then
> > > dd if=/usr/local/pgsql/iotest of=/dev/null
> > >
> > > If you run systat -vmstat 2 you will see 0% diskaccess during the read
> > > of the 2G file indicating that it has, in fact, been cached)
> >
> > Thank you for your reply. Does this apply to FreeBSD 5.4 or 6.0 on
> > amd64 (or both)?
> >
>
> Not sure about 6.0 (but I don't know why it would change) but definitely
> on 5.4 amd64 (and I would imagine i386 as well).

Works on FreeBSD 6.0 RC1 as well. Tried using count=4096 on a 1 GB ram
box. Same behaviour as you describe above.

regards
Claus