Heap usage

I haven't posted in a while, due to lack of time and too much work, and I think this post has been rather overdue.
One of the things aspects of AIX's malloc (or for that matter any other operating system) is that if you free the memory you have allocated, it won't reflect in the svmon output. This is because malloc subsystem caches the memory, to be used for further malloc.
An easy way to see how much memory your application is using (the memory malloced by it, + the memory in the free pool maintained by the malloc subsystem) is to use the variable process_brk which is exported by libc.
The way I usually go about it is to use the dbx subcommand
(dbx) p &process_brk
This gives me the address to dump, which I dump using a command similar to the one below
(dbx) 0x12345678/3X
This will give an output of three words..
12345678 12345678 1
The first word signifies what was the brk value before the first malloc was done, and the second word tells you what was the brk value after the second allocation was done. The third word tells how many sbrk()s were done. Of course, this gives me a very good estimate of the total memory used by my program.
Another benifit of this thing is to check for heap/stack collision. To check whether there has been a heap stack collision in my 32-bit app, what I normally do is to dump the stack-pointer, and check whether the stack_pointer falls within the process_brk minimum and maximum limits.
Hope this helps.