mincore

MINCORE(2)                  Linux Programmer's Manual                 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 to indicate the error.

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

COLOPHON
       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)