NAME

       malloc_trim - release free memory from the heap

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 attributes(7).

       ┌──────────────┬───────────────┬─────────┐
       │Interface     │ Attribute     │ Value   │
       ├──────────────┼───────────────┼─────────┤
       │malloc_trim() │ Thread safety │ MT-Safe │
       └──────────────┴───────────────┴─────────┘

CONFORMING TO

       This function is a GNU extension.

NOTES

       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

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

COLOPHON

       This  page  is  part of release 5.05 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 https://www.kernel.org/doc/man-pages/.