NAME
mincore
—
determine residency of memory
pages
LIBRARY
library “libc”
SYNOPSIS
#include
<sys/mman.h>
int
mincore
(const
void *addr, size_t
len, char
*vec);
DESCRIPTION
Themincore
()
system call determines whether each of the pages in the region beginning at
addr and continuing for len bytes
is resident or mapped, depending on the value of sysctl
vm.mincore_mapped. The status is returned in the
vec array, one character per page. Each character is
either 0 if the page is not resident, or a combination of the following flags
(defined in <sys/mman.h>
):
MINCORE_INCORE
- Page is in core (resident).
MINCORE_REFERENCED
- Page has been referenced by us.
MINCORE_MODIFIED
- Page has been modified by us.
MINCORE_REFERENCED_OTHER
- Page has been referenced.
MINCORE_MODIFIED_OTHER
- Page has been modified.
MINCORE_PSIND(i)
- Page is part of a large (“super”) page with size given by
index
i
in the array returned by getpagesizes(3). MINCORE_SUPER
- A mask of the valid
MINCORE_PSIND()
values. If any bits in this mask are set, the page is part of a large (“super”) page.
The information returned by
mincore
()
may be out of date by the time the system call returns. The only way to
ensure that a page is resident is to lock it into memory with the
mlock(2) system call.
If the vm.mincore_mapped sysctl is set to a
non-zero value (default), only the current process' mappings of the pages in
the specified virtual address range are examined. This does not preclude the
system from returning MINCORE_REFERENCED_OTHER
and
MINCORE_MODIFIED_OTHER
statuses. Otherwise, if the
sysctl value is zero, all resident pages backing the specified address range
are examined, regardless of the mapping state.
IMPLEMENTATION NOTES
Prior to the introduction of
MINCORE_PSIND()
in FreeBSD
13.0, MINCORE_SUPER
consisted of a single bit
equal to MINCORE_PSIND(1)
. In particular,
applications compiled using the old value of
MINCORE_SUPER
will not identify large pages with
size index 2 as being large pages.
RETURN VALUES
The mincore
() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno is set to indicate the
error.
ERRORS
The mincore
() system call will fail
if:
- [
ENOMEM
] - The virtual address range specified by the addr and len arguments is not fully mapped.
- [
EFAULT
] - The vec argument points to an illegal address.
SEE ALSO
madvise(2), mlock(2), mprotect(2), msync(2), munmap(2), getpagesize(3), getpagesizes(3)
HISTORY
The mincore
() system call first appeared
in 4.4BSD.