Name
readahead — perform file readahead into page
cache
Synopsis
#include <fcntl.h>
ssize_t readahead( |
int |
fd, |
| |
off64_t * |
offset, |
| |
size_t |
count); |
DESCRIPTION
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.
RETURN VALUE
On success, readahead()
returns 0; on failure, −1 is returned, with
errno set to indicate the cause
of the error.
ERRORS
- EBADF
-
fd is not a
valid file descriptor or is not open for reading.
- EINVAL
-
fd does not
refer to a file type to which readahead() can be applied.
VERSIONS
The readahead() system call
appeared in Linux 2.4.13; glibc support has been provided
since version 2.3.
CONFORMING TO
The readahead() system call
is Linux specific, and its use should be avoided in portable
applications.
SEE ALSO
fadvise(2), lseek(2), madvise(2), mmap(2), posix_fadvise(2), read(2)
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manual page may be incorrect or out-of-date.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-manpages@gmx.net>
2004-10-05 aeb, minor correction
|
