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



NAME
       remap_file_pages - create a nonlinear file mapping

SYNOPSIS
       #define _GNU_SOURCE         /* See feature_test_macros(7) */
       #include <sys/mman.h>

       int remap_file_pages(void *addr, size_t size, int prot,
                            size_t pgoff, int flags);

DESCRIPTION
       Note: this system call is (since Linux 3.16) deprecated and will eventually be replaced by
       a slower in-kernel emulation.  Those few applications that use  this  system  call  should
       consider migrating to alternatives.

       The  remap_file_pages() system call is used to create a nonlinear mapping, that is, a map‐
       ping in which the pages of the file are mapped into a nonsequential order in memory.   The
       advantage  of  using  remap_file_pages()  over using repeated calls to mmap(2) is that the
       former approach does not require the kernel to create additional VMA (Virtual Memory Area)
       data structures.

       To create a nonlinear mapping we perform the following steps:

       1. Use mmap(2) to create a mapping (which is initially linear).  This mapping must be cre‐
          ated with the MAP_SHARED flag.

       2. Use one or more calls to remap_file_pages() to rearrange the correspondence between the
          pages of the mapping and the pages of the file.  It is possible to map the same page of
          a file into multiple locations within the mapped region.

       The pgoff and size arguments specify the region of the file that is to be relocated within
       the  mapping:  pgoff is a file offset in units of the system page size; size is the length
       of the region in bytes.

       The addr argument serves two purposes.  First, it identifies the mapping  whose  pages  we
       want  to  rearrange.   Thus, addr must be an address that falls within a region previously
       mapped by a call to mmap(2).  Second, addr specifies the address at which the  file  pages
       identified by pgoff and size will be placed.

       The  values  specified  in  addr and size should be multiples of the system page size.  If
       they are not, then the kernel rounds both values down to the nearest multiple of the  page
       size.

       The prot argument must be specified as 0.

       The  flags argument has the same meaning as for mmap(2), but all flags other than MAP_NON‐
       BLOCK are ignored.

RETURN VALUE
       On success, remap_file_pages() returns 0.  On error, -1 is  returned,  and  errno  is  set
       appropriately.

ERRORS
       EINVAL addr does not refer to a valid mapping created with the MAP_SHARED flag.

       EINVAL addr, size, prot, or pgoff is invalid.

VERSIONS
       The  remap_file_pages()  system  call appeared in Linux 2.5.46; glibc support was added in
       version 2.3.3.

CONFORMING TO
       The remap_file_pages() system call is Linux-specific.

NOTES
       Since Linux 2.6.23, remap_file_pages() creates non-linear mappings only on in-memory  file
       systems  such  as  tmpfs,  hugetlbfs  or  ramfs.   On  filesystems  with  a backing store,
       remap_file_pages() is not much more efficient than using mmap(2) to adjust which parts  of
       the file are mapped to which addresses.

SEE ALSO
       getpagesize(2), mmap(2), mmap2(2), mprotect(2), mremap(2), msync(2)

COLOPHON
       This  page  is  part of release 3.74 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 http://www.kernel.org/doc/man-pages/.



Linux                                       2014-05-28                        REMAP_FILE_PAGES(2)