NAME

       mincore - determine whether pages are resident in memory

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #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

       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.

STANDARDS

       None.

HISTORY

       Linux 2.3.99pre1, glibc 2.2.

       First appeared in 4.4BSD.

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

BUGS

       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)).

SEE ALSO

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

Linux man-pages 6.7                                2023-10-31                                         mincore(2)