mincore(2) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | BUGS | SEE ALSO | COLOPHON

MINCORE(2)              Linux Programmer's Manual             MINCORE(2)

NAME         top

       mincore - determine whether pages are resident in memory

SYNOPSIS         top

       #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         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(_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         top

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

       Available since Linux 2.3.99pre1 and glibc 2.2.

CONFORMING TO         top

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

BUGS         top

       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         top

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

COLOPHON         top

       This page is part of release 5.11 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/.

Linux                          2021-03-22                     MINCORE(2)

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