Memory is NEVER freed...

[Jean-Eric Cuendet]

Hi,
First, if Im on the wrong list, please direct me to the good one please.
 
I have a problem. One of my program allocate a LOT of small pieces of memory 
with malloc.
When freed, the RSS of my prog doesnt change!
I *THINK* that the melmory is freed since if I alloc again the same space, the 
RSS doesnt cchange. But the RSS *NEVER* come back to the level it was before 
the allocation.
Ex: 
Alloc 50Mb => RSS=50Mb
Free 30MB=>RSS=50Mb
Free remaining 20Mb=>RSS=50Mb
!!!!
Alloc 30Mb=>RSS=50Mb
Alloc 30Mb=>RSS=60Mb
Free 60Mb=>RSS=60Mb
 
Why?
Is there a way to tell my prog to release not used pages?
 
Thanks for any help.
-jec