From: Daniel McNeil <daniel@osdl.org>
More testing on AIO with O_DIRECT and /dev/raw/. Doing AIO reads was
using a lot more cpu time than using dd on the raw partition even with
the io_queue_wait patch. Found out that aio is doing readahead even
for O_DIRECT. Here's a patch that fixes it.
fs/aio.c | 24 +++++++++++++++---------
1 files changed, 15 insertions(+), 9 deletions(-)
diff -puN fs/aio.c~aio-dio-no-readahead fs/aio.c
--- 25/fs/aio.c~aio-dio-no-readahead 2003-08-30 15:42:30.000000000 -0700
+++ 25-akpm/fs/aio.c 2003-08-30 15:42:30.000000000 -0700
@@ -1353,15 +1353,21 @@ ssize_t aio_setup_iocb(struct kiocb *kio
break;
ret = -EINVAL;
if (file->f_op->aio_read) {
- struct address_space *mapping =
- file->f_dentry->d_inode->i_mapping;
- unsigned long index = kiocb->ki_pos >> PAGE_CACHE_SHIFT;
- unsigned long end = (kiocb->ki_pos + kiocb->ki_left)
- >> PAGE_CACHE_SHIFT;
-
- for (; index < end; index++) {
- page_cache_readahead(mapping, &file->f_ra,
- file, index);
+ /*
+ * Do not do readahead for DIRECT i/o
+ */
+ if (!(file->f_flags & O_DIRECT)) {
+ struct address_space *mapping;
+ unsigned long index;
+ unsigned long end;
+
+ mapping = file->f_dentry->d_inode->i_mapping;
+ index = kiocb->ki_pos >> PAGE_CACHE_SHIFT;
+ end = (kiocb->ki_pos + kiocb->ki_left) >>
+ PAGE_CACHE_SHIFT;
+ for (; index < end; index++)
+ page_cache_readahead(mapping,
+ &file->f_ra, file, index);
}
kiocb->ki_retry = aio_pread;
}
_