mincore - determine whether pages are resident in memory
#include <unistd.h>
#include <sys/mman.h>
int mincore(void *addr, size_t length, unsigned
char *vec);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
mincore():
Since glibc 2.19:
_DEFAULT_SOURCE
Glibc 2.19 and earlier:
_BSD_SOURCE || _SVID_SOURCE
mincore() returns a vector that indicates whether pages of the calling
process's virtual memory are resident in core (RAM), and so will not cause a
disk access (page fault) if referenced. The kernel returns residency
information about the pages starting at the address
addr, and
continuing for
length bytes.
The
addr argument must be a multiple of the system page size. The
length argument need not be a multiple of the page size, but since
residency information is returned for whole pages,
length is
effectively rounded up to the next multiple of the page size. One may obtain
the page size (
PAGE_SIZE) using
sysconf(_SC_PAGESIZE).
The
vec argument must point to an array containing at least
(length+PAGE_SIZE-1) / PAGE_SIZE bytes. On return, the least
significant bit of each byte will be set if the corresponding page is
currently resident in memory, and be clear otherwise. (The settings of the
other bits in each byte are undefined; these bits are reserved for possible
later use.) Of course the information returned in
vec is only a
snapshot: pages that are not locked in memory can come and go at any moment,
and the contents of
vec may already be stale by the time this call
returns.
On success,
mincore() returns zero. On error, -1 is returned, and
errno is set appropriately.
EAGAIN kernel is temporarily out of resources.
- EFAULT
- vec points to an invalid address.
- EINVAL
- addr is not a multiple of the page size.
- ENOMEM
- length is greater than (TASK_SIZE - addr). (This
could occur if a negative value is specified for length, since that
value will be interpreted as a large unsigned integer.) In Linux 2.6.11
and earlier, the error EINVAL was returned for this condition.
- ENOMEM
- addr to addr + length contained unmapped memory.
Available since Linux 2.3.99pre1 and glibc 2.2.
mincore() is not specified in POSIX.1, and it is not available on all
UNIX implementations.
Before kernel 2.6.21,
mincore() did not return correct information for
MAP_PRIVATE mappings, or for nonlinear mappings (established using
remap_file_pages(2)).
fincore(1),
madvise(2),
mlock(2),
mmap(2),
posix_fadvise(2),
posix_madvise(3)