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(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 is not a multiple of the page size, or has a non-
positive value
EFAULT vec points to an illegal 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(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.
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(2), mmap(2)
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