malloc_trim(3) — Linux manual page


MALLOC_TRIM(3)            Linux Programmer's Manual           MALLOC_TRIM(3)

NAME         top

       malloc_trim - release free memory from the heap

SYNOPSIS         top

       #include <malloc.h>

       int malloc_trim(size_t pad);

DESCRIPTION         top

       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

RETURN VALUE         top

       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

ERRORS         top

       No errors are defined.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface     Attribute     Value   │
       │malloc_trim() │ Thread safety │ MT-Safe │

CONFORMING TO         top

       This function is a GNU extension.

NOTES         top

       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.

SEE ALSO         top

       sbrk(2), malloc(3), mallopt(3)

COLOPHON         top

       This page is part of release 5.07 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                            2019-05-09                   MALLOC_TRIM(3)

Pages that refer to this page: calloc(3)free(3)mallinfo(3)malloc(3)mallopt(3)realloc(3)reallocarray(3)