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 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 5.09 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                              2020-08-13                     MALLOC_TRIM(3)