malloc_trim(3) Library Functions Manual malloc_trim(3)
NAME
malloc_trim - release free memory from the heap
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <malloc.h>
int malloc_trim(size_t pad);
DESCRIPTION
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).
RETURN VALUE
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.
ERRORS
No errors are defined.
ATTRIBUTES
For an explanation of the terms used in this section, see attrib-
utes(7).
┌───────────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├───────────────────────────────────────────┼───────────────┼─────────┤
│ malloc_trim() │ Thread safety │ MT-Safe │
└───────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
GNU.
VERSIONS
glibc 2.0.
NOTES
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.
SEE ALSO
sbrk(2), malloc(3), mallopt(3)
Linux man-pages 6.7 2023-10-31 malloc_trim(3)
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