NAME
mincore - determine whether pages are resident in memory
SYNOPSIS
#include <unistd.h>
#include <sys/mman.h>
I int mincore(void * start , size_t length , unsigned char * vec );
DESCRIPTION
R 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
R start ,
and continuing for
length
bytes.
The
start
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
R 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.
RETURN VALUE
On success,
R mincore ()
returns zero.
On error, -1 is returned, and
errno
is set appropriately.
ERRORS
EAGAIN
kernel is temporarily out of resources.
EFAULT
vec
points to an invalid address.
EINVAL
start
is not a multiple of the page size.
ENOMEM
length
is greater than
(TASK_SIZE - start).
(This could occur if a negative value is specified for
R 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
start
to
start
+
length
contained unmapped memory.
VERSIONS
Available since Linux 2.3.99pre1 and glibc 2.2.
CONFORMING TO
R mincore ()
is not specified in POSIX.1-2001,
and it is not available on all Unix implementations.
BUGS
Before kernel 2.6.21,
R mincore ()
did not return correct information for
MAP_PRIVATE
mappings, or for non-linear mappings (established using
remap_file_pages(2)).
SEE ALSO
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