Name

mincore — determine whether pages are resident in memory

Synopsis

#include <unistd.h>
#include <sys/mman.h>
int mincore( void *  start,
  size_t   length,
  unsigned char *  vec);
[Note] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
mincore():
_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 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 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, 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_SIZEstart). (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

start to start + length contained unmapped memory.

VERSIONS

Available since Linux 2.3.99pre1 and glibc 2.2.

CONFORMING TO

mincore() is not specified in POSIX.1-2001, and it is not available on all Unix implementations.

BUGS

Before kernel 2.6.21, mincore() did not return correct information for MAP_PRIVATE mappings, or for non-linear mappings (established using remap_file_pages(2)).

SEE ALSO

mlock(2), mmap(2)

COLOPHON

This page is part of release 2.79 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


Copyright (C) 2001 Bert Hubert <ahuds9a.nl>
and Copyright (C) 2007 Michael Kerrisk <mtk.manpagesgmail.com>

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
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Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
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Formatted or processed versions of this manual, if unaccompanied by
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Created Sun Jun 3 17:23:32 2001 by bert hubert <ahuds9a.nl>
Slightly adapted, following comments by Hugh Dickins, aeb, 2001-06-04.
Modified, 20 May 2003, Michael Kerrisk <mtk.manpagesgmail.com>
Modified, 30 Apr 2004, Michael Kerrisk <mtk.manpagesgmail.com>
2005-04-05 mtk, Fixed error descriptions
after message from <gordon.jinintel.com>
2007-01-08 mtk, rewrote various parts