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  other-
       wise.   (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 nonlinear mappings
       (established using remap_file_pages(2)).

SEE ALSO
       mlock(2), mmap(2)

COLOPHON
       This page is part of release 3.25 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/.



Linux                                                      2008-04-22                                                 MINCORE(2)