readahead — perform file readahead into page cache
#define _GNU_SOURCE #include <fcntl.h>
ssize_t readahead( |
int | fd, |
| off64_t | offset, | |
| size_t | count); |
readahead() populates the
page cache with data from a file so that subsequent reads
from that file will not block on disk I/O. The fd argument is a file
descriptor identifying the file which is to be read. The
offset argument
specifies the starting point from which data is to be read
and count specifies
the number of bytes to be read. I/O is performed in whole
pages, so that offset
is effectively rounded down to a page boundary and bytes are
read up to the next page boundary greater than or equal to
(offset+count).
readahead() does not read
beyond the end of the file. readahead() blocks until the specified data
has been read. The current file offset of the open file
referred to by fd is
left unchanged.
On success, readahead()
returns 0; on failure, −1 is returned, with
errno set to indicate the cause
of the error.
fd is not a
valid file descriptor or is not open for reading.
fd does not
refer to a file type to which readahead() can be applied.
The readahead() system call
appeared in Linux 2.4.13; glibc support has been provided
since version 2.3.
The readahead() system call
is Linux-specific, and its use should be avoided in portable
applications.
This page is part of release 2.79 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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This manpage is Copyright (C) 2004, Michael Kerrisk 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 Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date.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. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. 2004-05-40 Created by Michael Kerrisk <mtk.manpagesgmail.com> 2004-10-05 aeb, minor correction |