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.
No errors are defined.
For an explanation of the terms used in this section, see
attributes(7).
| Interface |
Attribute |
Value |
| malloc_trim () |
Thread safety |
MT-Safe |
This function is a GNU extension.
This function is automatically called by
free(3) in certain
circumstances; see the discussion of
M_TOP_PAD and
M_TRIM_THRESHOLD in
mallopt(3).
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.
sbrk(2),
malloc(3),
mallopt(3)