Re: Tablespaces

On Thu, 2004-02-26 at 13:22, Gavin Sherry wrote:
> Postgres benefits a lot from kernel file system cache
> at the moment.

With the implementation of much smarter and more adaptive cache
replacement algorithm i.e. ARC, I would expect the benefit of using the
kernel file system cache to diminish significantly. It appears to me,
and I could be wrong, that the reason Postgres has depended on the
kernel file system cache isn't that this is obviously better in some
absolute sense (though it might be depending on the deployment
scenario), but that the original cache replacement algorithm in Postgres
was sufficiently poor that the better cache replacement algorithms in
the kernel cache more than offset any sub-optimality that might result
from doing so.

I would expect that with ARC and the redesign of some of the buffer
management bits for more scalability, you might very well get better
performance by allocating most of the memory to the buffer cache rather
than leaving it to the kernel file cache.

I'm actually fairly curious to see what the new buffer management scheme
will mean in terms of real world performance and parameter tuning.

-James Rogers
jrogers(at)neopolitan(dot)com