NAME¶

mincore — determine residency of memory pages

LIBRARY¶

Standard C Library (libc, -lc)

SYNOPSIS¶

#include <sys/mman.h>

int
mincore(const void *addr, size_t len, char *vec);

DESCRIPTION¶

The mincore() 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_SUPER

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The information returned by mincore() may be out of date by the time the system call returns.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.

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)

HISTORY¶

The mincore() system call first appeared in 4.4BSD.