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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)):

           Since glibc 2.19:
           Glibc 2.19 and earlier:
               _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


       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

       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,  and  it  is  not  available  on  all  UNIX


       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)).


       fincore(1), madvise(2), mlock(2), mmap(2), posix_fadvise(2), posix_madvise(3)


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