Open Source Software

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():
       Since glibc 2.19:
           _DEFAULT_SOURCE
       Glibc 2.19 and earlier:
           _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, 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 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at
   https://www.kernel.org/doc/man-pages/.



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