mincore

MINCORE(2)                 Linux Programmer's Manual                MINCORE(2)



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 following the start address. On return, the ker-
       nel 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(2).


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 start is not a multiple of the page size, or len has a non-posi-
              tive value

       EFAULT vec points to an invalid address

       ENOMEM address to address + length contained unmapped memory, 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(2) 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 Specifi-
       cation.

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

AVAILABILITY
       Since Linux 2.3.99pre1 and glibc 2.2.

SEE ALSO
       getpagesize(2), mmap(2)



Linux 2.4.5                       2001-06-03                        MINCORE(2)