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mincore() - Unix, Linux System Call
mincore - get information on whether pages are in core
int mincore(void *start, size_t length, unsigned char *vec);
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. (The other bits are undefined, reserved for possible
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.
mincore() to return successfully,
start must lie on a page boundary. It is the callers 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
mincore() returns zero.
On error, -1 is returned, and
errno is set appropriately.
EAGAIN kernel is temporarily out of resources
vec points to an invalid address
start is not a multiple of the page size.
len is greater than
(TASK_SIZE - start). (This could occur if a negative value is specified for
len, since that value will be interpreted as a large
In Linux 2.6.11 and earlier, the error
EINVAL was returned for this condition.
length contained unmapped memory, or memory not part of a file.
Up to now (Linux 2.6.5),
mincore() does not return correct information for MAP_PRIVATE mappings.
mincore() is not specified in POSIX.1-2001,
and it is not available on all Unix implementations.
mincore() function first appeared in 4.4BSD.
Since Linux 2.3.99pre1 and glibc 2.2.