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.