MINCORE(2)                FreeBSD System Calls Manual               MINCORE(2)

NAME
     mincore - determine residency of memory pages

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/mman.h>

     int
     mincore(const void *addr, size_t len, char *vec);

DESCRIPTION
     The mincore() system call determines whether each of the pages in the
     region beginning at addr and continuing for len bytes is resident or
     mapped, depending on the value of sysctl vm.mincore_mapped.  The status
     is returned in the vec array, one character per page.  Each character is
     either 0 if the page is not resident, or a combination of the following
     flags (defined in <sys/mman.h>):

     MINCORE_INCORE                Page is in core (resident).

     MINCORE_REFERENCED            Page has been referenced by us.

     MINCORE_MODIFIED              Page has been modified by us.

     MINCORE_REFERENCED_OTHER      Page has been referenced.

     MINCORE_MODIFIED_OTHER        Page has been modified.

     MINCORE_PSIND(i)              Page is part of a large ("super") page with
                                   size given by index i in the array returned
                                   by getpagesizes(3).

     MINCORE_SUPER                 A mask of the valid MINCORE_PSIND() values.
                                   If any bits in this mask are set, the page
                                   is part of a large ("super") page.

     The information returned by mincore() may be out of date by the time the
     system call returns.  The only way to ensure that a page is resident is
     to lock it into memory with the mlock(2) system call.

     If the vm.mincore_mapped sysctl is set to a non-zero value (default),
     only the current process' mappings of the pages in the specified virtual
     address range are examined.  This does not preclude the system from
     returning MINCORE_REFERENCED_OTHER and MINCORE_MODIFIED_OTHER statuses.
     Otherwise, if the sysctl value is zero, all resident pages backing the
     specified address range are examined, regardless of the mapping state.

IMPLEMENTATION NOTES
     Prior to the introduction of MINCORE_PSIND() in FreeBSD 13.0,
     MINCORE_SUPER consisted of a single bit equal to MINCORE_PSIND(1).  In
     particular, applications compiled using the old value of MINCORE_SUPER
     will not identify large pages with size index 2 as being large pages.

RETURN VALUES
     The mincore() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS
     The mincore() system call will fail if:

     [ENOMEM]           The virtual address range specified by the addr and
                        len arguments is not fully mapped.

     [EFAULT]           The vec argument points to an illegal address.

SEE ALSO
     madvise(2), mlock(2), mprotect(2), msync(2), munmap(2), getpagesize(3),
     getpagesizes(3)

HISTORY
     The mincore() system call first appeared in 4.4BSD.

FreeBSD 13.1-RELEASE-p6         August 23, 2020        FreeBSD 13.1-RELEASE-p6