mincore(2) - Linux manual page (original) (raw)

mincore(2) System Calls Manual mincore(2)

NAME top

   mincore - determine whether pages are resident in memory

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#include <sys/mman.h>**

   **int mincore(void** _addr_**[.**_length_**], 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 top

   **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(SCPAGESIZE)_.

   The _vec_ argument must point to an array containing at least
   _(length+PAGESIZE-1) / PAGESIZE_ 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 top

   On success, **mincore**() returns zero.  On error, -1 is returned, and
   _[errno](../man3/errno.3.html)_ is set to indicate the error.

ERRORS top

   **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 (_TASKSIZE_ - _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.

STANDARDS top

   None.

HISTORY top

   Linux 2.3.99pre1, glibc 2.2.

   First appeared in 4.4BSD.

   NetBSD, FreeBSD, OpenBSD, Solaris 8, AIX 5.1, SunOS 4.1.

BUGS top

   Before Linux 2.6.21, **mincore**() did not return correct information
   for **MAP_PRIVATE** mappings, or for nonlinear mappings (established
   using [remap_file_pages(2)](../man2/remap%5Ffile%5Fpages.2.html)).

SEE ALSO top

   [fincore(1)](../man1/fincore.1.html), [madvise(2)](../man2/madvise.2.html), [mlock(2)](../man2/mlock.2.html), [mmap(2)](../man2/mmap.2.html), [posix_fadvise(2)](../man2/posix%5Ffadvise.2.html),
   [posix_madvise(3)](../man3/posix%5Fmadvise.3.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23 mincore(2)

Pages that refer to this page:fincore(1), madvise(2), mlock(2), mmap(2), posix_fadvise(2), syscalls(2)