mincore(2) System Calls Manual mincore(2)
NAME
mincore - determine whether pages are resident in memory
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <sys/mman.h>
int mincore(void addr[.length], 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
DESCRIPTION
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 res-
idency 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 signifi-
cant bit of each byte will be set if the corresponding page is cur-
rently 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.
RETURN VALUE
On success, mincore() returns zero. On error, -1 is returned, and er-
rno is set to indicate the error.
ERRORS
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.
VERSIONS
Available since Linux 2.3.99pre1 and glibc 2.2.
STANDARDS
mincore() is not specified in POSIX.1, and it is not available on all
UNIX implementations.
BUGS
Before Linux 2.6.21, mincore() did not return correct information for
MAP_PRIVATE mappings, or for nonlinear mappings (established using
remap_file_pages(2)).
SEE ALSO
fincore(1), madvise(2), mlock(2), mmap(2), posix_fadvise(2), posix_mad-
vise(3)
Linux man-pages 6.03 2023-02-05 mincore(2)
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