cfq-iosched: improve continue or break logic in cfq_dispatch

This improves performance considerably for sync requests when you
have command queuing enabled.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 8 insertions, 8 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 6aa5523f514c..b6491c020f26 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1057,6 +1057,14 @@ cfq_dispatch_requests(request_queue_t *q, int force)
                 if (prev_cfqq == cfqq)
                         break;
 
+                /*
+                 * So we have dispatched before in this round, if the
+                 * next queue has idling enabled (must be sync), don't
+                 * allow it service until the previous have continued.
+                 */
+                if (cfqd->rq_in_driver && cfq_cfqq_idle_window(cfqq))
+                        break;
+
                 cfq_clear_cfqq_must_dispatch(cfqq);
                 cfq_clear_cfqq_wait_request(cfqq);
                 del_timer(&cfqd->idle_slice_timer);
@@ -1066,14 +1074,6 @@ cfq_dispatch_requests(request_queue_t *q, int force)
                         max_dispatch = 1;
 
                 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
-
-                /*
-                 * If the dispatch cfqq has idling enabled and is still
-                 * the active queue, break out.
-                 */
-                if (cfq_cfqq_idle_window(cfqq) && cfqd->active_queue)
-                        break;
-
                 prev_cfqq = cfqq;
         }