mincore - get information on whether pages are in core
#include <unistd.h>
#include <sys/mman.h>
int mincore(void *start, size_t length, unsigned char * vec);
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 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).
On success, mincore returns zero. On error, -1 is returned, and errno
is set appropriately.
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 memory, or memory
not part of a file.
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.
The mincore() function first appeared in 4.4BSD.
Since Linux 2.3.99pre1 and glibc 2.2.
getpagesize(2), mmap(2)
Linux 2.4.5 2001-06-03 MINCORE(2)
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