1 .\" Copyright (C) 2003, Michael Kerrisk (mtk.manpages@gmail.com)
3 .\" %%%LICENSE_START(VERBATIM)
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25 .\" 2003-12-10 Initial creation, Michael Kerrisk <mtk.manpages@gmail.com>
26 .\" 2004-10-28 aeb, corrected prototype, prot must be 0
28 .TH REMAP_FILE_PAGES 2 2014-05-28 "Linux" "Linux Programmer's Manual"
30 remap_file_pages \- create a nonlinear file mapping
33 .BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */"
34 .B #include <sys/mman.h>
36 .BI "int remap_file_pages(void *" addr ", size_t " size ", int " prot ,
37 .BI " size_t " pgoff ", int " flags );
41 .\" commit 33041a0d76d3c3e0aff28ac95a2ffdedf1282dbc
42 .\" http://lwn.net/Articles/597632/
43 this system call is (since Linux 3.16) deprecated and will
44 eventually be replaced by a slower in-kernel emulation.
45 Those few applications that use this system call should
46 consider migrating to alternatives.
49 .BR remap_file_pages ()
50 system call is used to create a nonlinear mapping, that is, a mapping
51 in which the pages of the file are mapped into a nonsequential order
53 The advantage of using
54 .BR remap_file_pages ()
55 over using repeated calls to
57 is that the former approach does not require the kernel to create
58 additional VMA (Virtual Memory Area) data structures.
60 To create a nonlinear mapping we perform the following steps:
65 to create a mapping (which is initially linear).
66 This mapping must be created with the
71 Use one or more calls to
72 .BR remap_file_pages ()
73 to rearrange the correspondence between the pages of the mapping
74 and the pages of the file.
75 It is possible to map the same page of a file
76 into multiple locations within the mapped region.
82 arguments specify the region of the file that is to be relocated
85 is a file offset in units of the system page size;
87 is the length of the region in bytes.
91 argument serves two purposes.
92 First, it identifies the mapping whose pages we want to rearrange.
95 must be an address that falls within
96 a region previously mapped by a call to
100 specifies the address at which the file pages
107 The values specified in
111 should be multiples of the system page size.
112 If they are not, then the kernel rounds
116 to the nearest multiple of the page size.
117 .\" This rounding is weird, and not consistent with the treatment of
118 .\" the analogous arguments for munmap()/mprotect() and for mlock().
123 argument must be specified as 0.
127 argument has the same meaning as for
129 but all flags other than
134 .BR remap_file_pages ()
136 On error, \-1 is returned, and
138 is set appropriately.
143 does not refer to a valid mapping
155 .\" And possibly others from vma->vm_ops->populate()
158 .BR remap_file_pages ()
159 system call appeared in Linux 2.5.46;
160 glibc support was added in version 2.3.3.
163 .BR remap_file_pages ()
164 system call is Linux-specific.
167 .\" commit 3ee6dafc677a68e461a7ddafc94a580ebab80735
168 .BR remap_file_pages ()
169 creates non-linear mappings only
170 on in-memory file systems such as tmpfs, hugetlbfs or ramfs.
171 On filesystems with a backing store,
172 .BR remap_file_pages ()
173 is not much more efficient than using
175 to adjust which parts of the file are mapped to which addresses.
184 This page is part of release 3.78 of the Linux
187 A description of the project,
188 information about reporting bugs,
189 and the latest version of this page,
191 \%http://www.kernel.org/doc/man\-pages/.