remap_file_pages(2)

1REMAP_FILE_PAGES(2)        Linux Programmer's Manual       REMAP_FILE_PAGES(2)
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NAME

6       remap_file_pages - create a non-linear file mapping
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SYNOPSIS

9       #define _GNU_SOURCE
10       #include <sys/mman.h>
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12       int remap_file_pages(void *start, size_t size, int prot,
13                            ssize_t pgoff, int flags);
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DESCRIPTION

16       The  remap_file_pages() system call is used to create a non-linear map‐
17       ping, that is, a mapping in which the pages of the file are mapped into
18       a   non-sequential   order   in   memory.    The   advantage  of  using
19       remap_file_pages() over using repeated calls to  mmap(2)  is  that  the
20       former  approach  does  not require the kernel to create additional VMA
21       (Virtual Memory Area) data structures.
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23       To create a non-linear mapping we perform the following steps:
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25       1.     Use mmap() to create a  mapping  (which  is  initially  linear).
26              This mapping must be created with the MAP_SHARED flag.
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28       2.     Use  one  or  more  calls to remap_file_pages() to rearrange the
29              correspondence between the pages of the mapping and the pages of
30              the  file.   It  is possible to map the same page of a file into
31              multiple locations within the mapped region.
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33       The pgoff and size arguments specify the region of the file that is  to
34       be relocated within the mapping: pgoff is a file offset in units of the
35       system page size; size is the length of the region in bytes.
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37       The start argument serves two purposes.  First, it identifies the  map‐
38       ping  whose pages we want to rearrange.  Thus, start must be an address
39       that falls within a region previously mapped by a call to mmap().  Sec‐
40       ond,  start specifies the address at which the file pages identified by
41       pgoff and size will be placed.
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43       The values specified in start and size should be multiples of the  sys‐
44       tem  page  size.   If  they are not, then the kernel rounds both values
45       down to the nearest multiple of the page size.
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47       The prot argument must be specified as 0.
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49       The flags argument has the same meaning as for mmap(),  but  all  flags
50       other than MAP_NONBLOCK are ignored.
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RETURN VALUE

53       On  success,  remap_file_pages()  returns 0.  On error, -1 is returned,
54       and errno is set appropriately.
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NOTES

57       The remap_file_pages() system call appeared in Linux 2.5.46.
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ERRORS

60       EINVAL start does not  refer  to  a  valid  mapping  created  with  the
61              MAP_SHARED flag.
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63       EINVAL start, size, prot, or pgoff is invalid.
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CONFORMING TO

66       The remap_file_pages() system call is Linux specific.
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