|MALLOC_TRIM(3)||Linux Programmer's Manual||MALLOC_TRIM(3)|
int malloc_trim(size_t pad);
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).
|malloc_trim ()||Thread safety||MT-Safe|
Only the main heap (using sbrk(2)) honors the pad argument; thread heaps do not.
Since glibc 2.8 this function frees memory in all arenas and in all chunks with whole free pages.
Before glibc 2.8 this function only freed memory at the top of the heap in the main arena.