1 files changed, 16 insertions, 2 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 8917f2b3a783..70b48ea0e3e9 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -181,6 +181,8 @@ struct cfq_data {
          * Fallback dummy cfqq for extreme OOM conditions
          */
         struct cfq_queue oom_cfqq;
+
+        unsigned long last_end_sync_rq;
 };
 
 enum cfqq_state_flags {
@@ -1314,6 +1316,8 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
          * Does this cfqq already have too much IO in flight?
          */
         if (cfqq->dispatched >= max_dispatch) {
+                unsigned long load_at = cfqd->last_end_sync_rq + cfq_slice_sync;
+
                 /*
                  * idle queue must always only have a single IO in flight
                  */
@@ -1327,6 +1331,14 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
                         return 0;
 
                 /*
+                 * If a sync request has completed recently, don't overload
+                 * the dispatch queue yet with async requests.
+                 */
+                if (cfqd->cfq_desktop && !cfq_cfqq_sync(cfqq)
+                    && time_before(jiffies, load_at))
+                        return 0;
+
+                /*
                  * we are the only queue, allow up to 4 times of 'quantum'
                  */
                 if (cfqq->dispatched >= 4 * max_dispatch)
@@ -2158,8 +2170,10 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
         if (cfq_cfqq_sync(cfqq))
                 cfqd->sync_flight--;
 
-        if (sync)
+        if (sync) {
                 RQ_CIC(rq)->last_end_request = now;
+                cfqd->last_end_sync_rq = now;
+        }
 
         /*
          * If this is the active queue, check if it needs to be expired,
@@ -2483,7 +2497,7 @@ static void *cfq_init_queue(struct request_queue *q)
         cfqd->cfq_slice_idle = cfq_slice_idle;
         cfqd->cfq_desktop = 1;
         cfqd->hw_tag = 1;
-
+        cfqd->last_end_sync_rq = jiffies;
         return cfqd;
 }