aio: implement request batching
Hi,
Some workloads issue batches of small I/O, and the performance is poor
due to the call to blk_run_address_space for every single iocb. Nathan
Roberts pointed this out, and suggested that by deferring this call
until all I/Os in the iocb array are submitted to the block layer, we
can realize some impressive performance gains (up to 30% for sequential
4k reads in batches of 16).
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fs/direct-io.c b/fs/direct-io.c
index c86d35f..3af761c 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1028,9 +1028,6 @@
if (dio->bio)
dio_bio_submit(dio);
- /* All IO is now issued, send it on its way */
- blk_run_address_space(inode->i_mapping);
-
/*
* It is possible that, we return short IO due to end of file.
* In that case, we need to release all the pages we got hold on.
@@ -1057,8 +1054,11 @@
((rw & READ) || (dio->result == dio->size)))
ret = -EIOCBQUEUED;
- if (ret != -EIOCBQUEUED)
+ if (ret != -EIOCBQUEUED) {
+ /* All IO is now issued, send it on its way */
+ blk_run_address_space(inode->i_mapping);
dio_await_completion(dio);
+ }
/*
* Sync will always be dropping the final ref and completing the