remap_file_pages


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

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

DESCRIPTION
       The  remap_file_pages()  system call is used to create a nonlinear map-
       ping, that is, a mapping 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 created with the MAP_SHARED flag.

       2. Use  one or more calls to remap_file_pages() to rearrange the corre-
          spondence 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  map-
       ping  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_NONBLOCK 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.
       This page is part of release 3.35 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://man7.org/linux/man-pages/.



Linux                             2008-04-22               REMAP_FILE_PAGES(2)
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