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remap_file_pages — create a nonlinear file mapping
#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); |
The remap_file_pages()
system call is used to create a nonlinear mapping, 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:
Use mmap(2) to create a
mapping (which is initially linear). This mapping must
be created with the MAP_SHARED flag.
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_NONBLOCK are
ignored.
On success, remap_file_pages() returns 0. On error,
−1 is returned, and errno
is set appropriately.
addr does
not refer to a valid mapping created with the
MAP_SHARED flag.
addr,
size,
prot, or
pgoff is
invalid.
The remap_file_pages()
system call appeared in Linux 2.5.46; glibc support was added
in version 2.3.3.
This page is part of release 3.52 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man−pages/.
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Copyright (C) 2003, Michael Kerrisk (mtk.manpagesgmail.com) %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END 2003-12-10 Initial creation, Michael Kerrisk <mtk.manpagesgmail.com> 2004-10-28 aeb, corrected prototype, prot must be 0 |