[PATCH] aio: optimize io_submit_one()
This patch optimizes io_submit_one to call aio_run_iocb() directly if
ctx->run_list is empty. When the list is empty, the operation of adding to
the list, then call to __aio_run_iocbs() is unnecessary because these
operations are done in one atomic step. ctx->run_list always has only one
element in this case. This optimization speeds up industry standard db
transaction processing benchmark by 0.2%.
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Suparna Bhattacharya <suparna@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/aio.c b/fs/aio.c
index 674bb47..7afa222 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1514,10 +1514,14 @@
goto out_put_req;
spin_lock_irq(&ctx->ctx_lock);
- list_add_tail(&req->ki_run_list, &ctx->run_list);
- /* drain the run list */
- while (__aio_run_iocbs(ctx))
- ;
+ if (likely(list_empty(&ctx->run_list))) {
+ aio_run_iocb(req);
+ } else {
+ list_add_tail(&req->ki_run_list, &ctx->run_list);
+ /* drain the run list */
+ while (__aio_run_iocbs(ctx))
+ ;
+ }
spin_unlock_irq(&ctx->ctx_lock);
aio_put_req(req); /* drop extra ref to req */
return 0;