mincore(2)

1mincore(2)                    System Calls Manual                   mincore(2)
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NAME

6       mincore - determine whether pages are resident in memory
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <sys/mman.h>
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14       int mincore(void addr[.length], size_t length, unsigned char *vec);
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16   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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18       mincore():
19           Since glibc 2.19:
20               _DEFAULT_SOURCE
21           glibc 2.19 and earlier:
22               _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

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

48       On  success, mincore() returns zero.  On error, -1 is returned, and er‐
49       rno is set to indicate the error.
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ERRORS

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

66       None.
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HISTORY

69       Linux 2.3.99pre1, glibc 2.2.
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71       First appeared in 4.4BSD.
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73       NetBSD, FreeBSD, OpenBSD, Solaris 8, AIX 5.1, SunOS 4.1.
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BUGS

76       Before  Linux  2.6.21, mincore() did not return correct information for
77       MAP_PRIVATE mappings, or  for  nonlinear  mappings  (established  using
78       remap_file_pages(2)).
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