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MINCORE(2)		       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 re-
     gion 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  getpa-
			       gesizes(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     The  information  returned  by mincore() may be out of date by the time the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  ad-
     dress 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, appli-
     cations  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 ports 15.quarterly	 August 23, 2020		      MINCORE(2)

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