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       mincore - determine whether pages are resident in memory


       #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


       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.


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


       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.


       Available since Linux 2.3.99pre1 and glibc 2.2.


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


       Before kernel 2.6.21, mincore() did not return correct information  for
       MAP_PRIVATE  mappings,  or  for  nonlinear  mappings (established using


       mlock(2), mmap(2)


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