MINCORE(E)          Linux Programmer's Manual          MINCORE(E)



NAME
       mincore - get information on whether pages are in core

SYNOPSIS
       #include <unistd.h>
       #include <sys/mman.h>

       int  mincore(void  *start,  size_t  length,  unsigned char
       *vec);

DESCRIPTION
       The mincore function requests a  vector  describing  which
       pages  of  a file are in core and can be read without disk
       access. The kernel will supply data for length bytes  fol-
       lowing  the start address. On return, the kernel will have
       filled vec with bytes, of which the least significant  bit
       indicates if a page is core resident.

       For  mincore  to  return successfully, start must lie on a
       page boundary. It is the caller's responsibility to  round
       up to the nearest page. The length parameter need not be a
       multiple of the page size. The vector vec  must  be  large
       enough  to contain length/PAGE_SIZE bytes.  One may obtain
       the page size from getpagesize(e).


RETURN VALUE
       On  success,  mincore  returns  zero.   On  error,  -1  is
       returned, and errno is set appropriately.

ERRORS
       EAGAIN kernel is temporarily out of resources

       EINVAL is  not  a multiple of the page size, or has a non-
              positive value

       EFAULT vec points to an invalid address

       ENOMEM address to address + length contained unmapped mem-
              ory, or memory not part of a file.


BUGS
       mincore  should return a bit vector and not a byte vector.
       As of Linux 2.4.5, it is not possible to gain  information
       on  the  core residency of pages which are not backed by a
       file.  In  other  words,  calling  mincore  on  an  region
       returned  by  an  anonymous mmap(p) does not work and sets
       errno to ENOMEM. Unless pages are locked  in  memory,  the
       contents  of  vec  may  be  stale  by  the time they reach
       userspace.


CONFORMING TO
       mincore does not appear to be part of POSIX or the  Single
       Unix Specification.

HISTORY
       The mincore() function first appeared in 4.4BSD.

AVAILABILITY
       Since Linux 2.3.99pre1 and glibc 2.2.

SEE ALSO
       getpagesize(e), mmap(p)



Linux 2.4.5                 2001-06-03                 MINCORE(E)