On Solaris continous memory allocation doesn't reduced image size

On Solaris continous memory allocation doesn't reduced image size

I have written one test program on Solaris sparc server and compiled it
using Sun Studio
#include <iostream>
using namespace std;
int main()
{
const int size = 9999;
char *ptr[size];
while(1)
{
for(int i = 0; i < size; i++)
{
ptr[i] = new char[2048];
}
for(int i = 0; i < size; i++)
{
delete[] ptr[i];
}
}
return 9;
}
compiled it as
CC -m64 -g
Now when I run it I can see that process size keeps on increasing and
process crashes when it reached system memory limit. I traced it using
truss and I can only see brk system calls. On searching some oracle sites
I set LD_PRELOAD=libmapmalloc.so and then process size was constant. truss
shows that this time it was using malloc to map anonymous memory pages.
On other hand I tried to see this behavioud on RHEL Linux 2.6 x86 box as
well and there too it used truss but process size was constant.
I don't understand behaviour or Solaris in first case where it uses brk to
increase size of data segment but when I do a delete it didn't reduced it.
Can somebody please explain me why solaris is doing this way ?
So what different is linux doing here to keep process size constant as it
also uses same system call.
Thanks Niraj Rathi