malloc_trim - release free memory from the heap
#include <malloc.h>
int malloc_trim(size_t pad);The malloc_trim() function attempts to release free memory from the heap (by calling sbrk(2) or madvise(2) with suitable arguments).
The pad argument specifies the amount of free space to leave
untrimmed at the top of the heap. If this argument is 0, only the
minimum amount of memory is maintained at the top of the heap (i.e., one
page or less). A nonzero argument can be used to maintain some trailing
space at the top of the heap in order to allow future allocations to be
made without having to extend the heap with
sbrk(2).
The malloc_trim() function returns 1 if memory was actually released back to the system, or 0 if it was not possible to release any memory.