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 main‐
       tained 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
       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                                                                          2021-03-22                                                                 MALLOC_TRIM(3)