1REMAP_FILE_PAGES(2) Linux Programmer's Manual REMAP_FILE_PAGES(2)
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6 remap_file_pages - create a nonlinear file mapping
7
9 #define _GNU_SOURCE /* See feature_test_macros(7) */
10 #include <sys/mman.h>
11 int remap_file_pages(void *addr, size_t size, int prot,
13 size_t pgoff, int flags);
14
16 Note: this system call was marked as deprecated starting with Linux
17 3.16. In Linux 4.0, the implementation was replaced by a slower in-
18 kernel emulation. Those few applications that use this system call
19 should consider migrating to alternatives. This change was made
20 because the kernel code for this system call was complex, and it is
21 believed to be little used or perhaps even completely unused. While it
22 had some use cases in database applications on 32-bit systems, those
23 use cases don't exist on 64-bit systems.
24 The remap_file_pages() system call is used to create a nonlinear map‐
26 ping, that is, a mapping in which the pages of the file are mapped into
27 a nonsequential order in memory. The advantage of using
28 remap_file_pages() over using repeated calls to mmap(2) is that the
29 former approach does not require the kernel to create additional VMA
30 (Virtual Memory Area) data structures.
31 To create a nonlinear mapping we perform the following steps:
33 1. Use mmap(2) to create a mapping (which is initially linear). This
35 mapping must be created with the MAP_SHARED flag.
36 2. Use one or more calls to remap_file_pages() to rearrange the corre‐
38 spondence between the pages of the mapping and the pages of the
39 file. It is possible to map the same page of a file into multiple
40 locations within the mapped region.
41 The pgoff and size arguments specify the region of the file that is to
43 be relocated within the mapping: pgoff is a file offset in units of the
44 system page size; size is the length of the region in bytes.
45 The addr argument serves two purposes. First, it identifies the map‐
47 ping whose pages we want to rearrange. Thus, addr must be an address
48 that falls within a region previously mapped by a call to mmap(2).
49 Second, addr specifies the address at which the file pages identified
50 by pgoff and size will be placed.
51 The values specified in addr and size should be multiples of the system
53 page size. If they are not, then the kernel rounds both values down to
54 the nearest multiple of the page size.
55 The prot argument must be specified as 0.
57 The flags argument has the same meaning as for mmap(2), but all flags
59 other than MAP_NONBLOCK are ignored.
60
62 On success, remap_file_pages() returns 0. On error, -1 is returned,
63 and errno is set appropriately.
64
66 EINVAL addr does not refer to a valid mapping created with the
67 MAP_SHARED flag.
68 EINVAL addr, size, prot, or pgoff is invalid.
70
72 The remap_file_pages() system call appeared in Linux 2.5.46; glibc sup‐
73 port was added in version 2.3.3.
74
76 The remap_file_pages() system call is Linux-specific.
77
79 Since Linux 2.6.23, remap_file_pages() creates non-linear mappings only
80 on in-memory filesystems such as tmpfs(5), hugetlbfs or ramfs. On
81 filesystems with a backing store, remap_file_pages() is not much more
82 efficient than using mmap(2) to adjust which parts of the file are
83 mapped to which addresses.
84
86 getpagesize(2), mmap(2), mmap2(2), mprotect(2), mremap(2), msync(2)
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89 This page is part of release 4.15 of the Linux man-pages project. A
90 description of the project, information about reporting bugs, and the
91 latest version of this page, can be found at
92 https://www.kernel.org/doc/man-pages/.
93Linux 2017-09-15 REMAP_FILE_PAGES(2)