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 kernel will have filled vec with bytes, of which the least signif-
       icant  bit  indicates  if a page is core resident. (The other bits are
       undefined, reserved for possible later use.)  Of course this is only a
       snapshot	 -  pages  that	 are  not  locked in core can come and go any
       moment, and the contents of vec may be stale already  when  this	 call
       returns.

       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-1)	 /  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-pos-
	      itive value

       EFAULT vec points to an invalid address

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


BUGS
       Up to now (Linux 2.6.5), mincore does not return	 correct  information
       for MAP_PRIVATE mappings.


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

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

AVAILABILITY
       Since Linux 2.3.99pre1 and glibc 2.2.

SEE ALSO
       getpagesize(2), mlock(2), mmap(2)



Linux 2.6.5			  2004-04-30			   MINCORE(2)