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

NAME
       mincore - determine whether pages are resident in memory

SYNOPSIS
       #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_PA‐
       GESIZE).

       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)

Linux                                                                          2021-03-22                                                                     MINCORE(2)