mincore(2) — Linux manual page


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)):

           Since glibc 2.19:
           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 appropriately.

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

       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),

COLOPHON         top

       This page is part of release 5.08 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

Linux                            2017-09-15                       MINCORE(2)

Pages that refer to this page: fincore(1)arm_fadvise(2)arm_fadvise64_64(2)fadvise64(2)fadvise64_64(2)madvise(2)mlock2(2)mlock(2)mlockall(2)mmap(2)munlock(2)munlockall(2)munmap(2)posix_fadvise(2)syscalls(2)mmap64(3)