mincore(2)

1MINCORE(2)                 Linux Programmer's Manual                MINCORE(2)
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NAME

6       mincore - determine whether pages are resident in memory
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SYNOPSIS

9       #include <unistd.h>
10       #include <sys/mman.h>
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12       int mincore(void *addr, size_t length, unsigned char *vec);
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14   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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16       mincore(): _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

19       mincore()  returns a vector that indicates whether pages of the calling
20       process's virtual memory are resident in core (RAM), and  so  will  not
21       cause  a  disk  access  (page fault) if referenced.  The kernel returns
22       residency information about the pages starting at the address addr, and
23       continuing for length bytes.
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25       The  addr  argument  must  be  a multiple of the system page size.  The
26       length argument need not be a multiple of the page size, but since res‐
27       idency  information  is returned for whole pages, length is effectively
28       rounded up to the next multiple of the page size.  One may  obtain  the
29       page size (PAGE_SIZE) using sysconf(_SC_PAGESIZE).
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31       The   vec   argument  must  point  to  an  array  containing  at  least
32       (length+PAGE_SIZE-1) / PAGE_SIZE bytes.  On return, the least  signifi‐
33       cant  bit  of  each  byte will be set if the corresponding page is cur‐
34       rently resident in memory, and be clear otherwise.   (The  settings  of
35       the  other bits in each byte are undefined; these bits are reserved for
36       possible later use.)  Of course the information returned in vec is only
37       a  snapshot: pages that are not locked in memory can come and go at any
38       moment, and the contents of vec may already be stale by the  time  this
39       call returns.
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RETURN VALUE

42       On  success,  mincore()  returns  zero.   On error, -1 is returned, and
43       errno is set appropriately.
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ERRORS

46       EAGAIN kernel is temporarily out of resources.
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48       EFAULT vec points to an invalid address.
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50       EINVAL addr is not a multiple of the page size.
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52       ENOMEM length is greater than (TASK_SIZE - addr).  (This could occur if
53              a  negative value is specified for length, since that value will
54              be interpreted as a large unsigned integer.)   In  Linux  2.6.11
55              and earlier, the error EINVAL was returned for this condition.
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57       ENOMEM addr to addr + length contained unmapped memory.
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VERSIONS

60       Available since Linux 2.3.99pre1 and glibc 2.2.
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CONFORMING TO

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

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

75       This page is part of release 3.22 of the Linux  man-pages  project.   A
76       description  of  the project, and information about reporting bugs, can
77       be found at http://www.kernel.org/doc/man-pages/.
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81Linux                             2008-04-22                        MINCORE(2)