NAME
readahead - perform file readahead into page cache
SYNOPSIS
#include <fcntl.h>
I ssize_t readahead(int fd , off64_t * offset , size_t count );
DESCRIPTION
R 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
R (offset+count) .
R readahead ()
does not read beyond the end of the file.
R 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,
R 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
R readahead ()
can be applied.
VERSIONS
The
R readahead ()
system call appeared in Linux 2.4.13;
glibc support has been provided since version 2.3.
CONFORMING TO
The
R readahead ()
system call is Linux specific, and its use should be avoided
in portable applications.
SEE ALSO
ČLÁNKY DO MAILU