malloc_trim

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

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  at-
       tributes(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 circum-
       stances; see the discussion of M_TOP_PAD and M_TRIM_THRESHOLD  in  mal-
       lopt(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/.

Linux                             2019-05-09                    MALLOC_TRIM(3)