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



NAME
       mincore - determine whether pages are resident in memory

SYNOPSIS
       #include <unistd.h>
       #include <sys/mman.h>

       int mincore(void *addr, size_t length, unsigned char *vec);

   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 addr, and continuing for length bytes.

       The  addr  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 addr is not a multiple of the page size.

       ENOMEM length is greater than (TASK_SIZE - addr).  (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 addr to addr + 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 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2008-04-22                        MINCORE(2)