postgres memory management

Hi all,

I'm experiencing some strange behaviour with postgresql 7.0.3 on Red Hat
Linux 7. I'm sending lots of insert statements to the postgresql server
from another machine via JDBC. During that process postgresql continues to
take up more and more memory and seemingly never returns it to the system.
Oddly if I watch the postmaster and it's sub processes in ktop, I can't see
which process takes up this memory. ktop shows that the postgresql related
processes have a constant memory usage but the overall memory usage always
increases as long as I continue to send insert statements.

When the database connection is closed, no memory is reclaimed, the overall
memory usage stays the same. And when I close down all postgresql processes
including postmaster, it's the same.
I'm rather new to Linux and postgresql so I'm not sure if I should call
this a memory leak :-)
Has anybody experienced a similar thing?

thanks,
Alexander Jerusalemvknn