diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 838834b..ef59ab3 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -83,9 +83,14 @@ struct cfq_rb_root {
 	unsigned total_weight;
 	u64 min_vdisktime;
 	struct rb_node *active;
+	unsigned long last_end_request;
+	unsigned long ttime_total;
+	unsigned long ttime_samples;
+	unsigned long ttime_mean;
 };
 #define CFQ_RB_ROOT	(struct cfq_rb_root) { .rb = RB_ROOT, .left = NULL, \
-			.count = 0, .min_vdisktime = 0, }
+			.count = 0, .min_vdisktime = 0, .last_end_request = 0, \
+			.ttime_total = 0, .ttime_samples = 0, .ttime_mean = 0 }
 
 /*
  * Per process-grouping structure
@@ -962,8 +967,10 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
 		goto done;
 
 	cfqg->weight = blkcg->weight;
-	for_each_cfqg_st(cfqg, i, j, st)
+	for_each_cfqg_st(cfqg, i, j, st) {
 		*st = CFQ_RB_ROOT;
+		st->last_end_request = jiffies;
+	}
 	RB_CLEAR_NODE(&cfqg->rb_node);
 
 	/*
@@ -1795,9 +1802,12 @@ static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 
 	/*
 	 * Otherwise, we do only if they are the last ones
-	 * in their service tree.
+	 * in their service tree and the average think time is
+	 * less than the slice length.
 	 */
-	if (service_tree->count == 1 && cfq_cfqq_sync(cfqq))
+	if (service_tree->count == 1 && cfq_cfqq_sync(cfqq) &&
+	    (!sample_valid(service_tree->ttime_samples || 
+	     cfqq->slice_end - jiffies < service_tree->ttime_mean)))
 		return 1;
 	cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d",
 			service_tree->count);
@@ -2988,6 +2998,18 @@ err:
 }
 
 static void
+cfq_update_st_thinktime(struct cfq_data *cfqd, struct cfq_rb_root *service_tree)
+{
+	unsigned long elapsed = jiffies - service_tree->last_end_request;
+	unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
+
+	service_tree->ttime_samples = (7*service_tree->ttime_samples + 256) / 8;
+	service_tree->ttime_total = (7*service_tree->ttime_total + 256*ttime)/8;
+	service_tree->ttime_mean = (service_tree->ttime_total + 128) /
+						service_tree->ttime_samples;
+}
+
+static void
 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
 {
 	unsigned long elapsed = jiffies - cic->last_end_request;
@@ -3166,6 +3188,7 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 		cfqq->meta_pending++;
 
 	cfq_update_io_thinktime(cfqd, cic);
+	cfq_update_st_thinktime(cfqd, cfqq->service_tree);
 	cfq_update_io_seektime(cfqd, cfqq, rq);
 	cfq_update_idle_window(cfqd, cfqq, cic);
 
@@ -3304,7 +3327,16 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
 	cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
 
 	if (sync) {
+		struct cfq_rb_root *st;
+
 		RQ_CIC(rq)->last_end_request = now;
+		/*
+		 * cfqq->service_tree is only filled in while on the rb tree,
+		 * so we need to lookup the service tree here.
+		 */
+		st = service_tree_for(cfqq->cfqg,
+				      cfqq_prio(cfqq), cfqq_type(cfqq));
+		st->last_end_request = now;
 		if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
 			cfqd->last_delayed_sync = now;
 	}
@@ -3678,11 +3710,14 @@ static void *cfq_init_queue(struct request_queue *q)
 
 	/* Init root service tree */
 	cfqd->grp_service_tree = CFQ_RB_ROOT;
+	cfqd->grp_service_tree.last_end_request = jiffies;
 
 	/* Init root group */
 	cfqg = &cfqd->root_group;
-	for_each_cfqg_st(cfqg, i, j, st)
+	for_each_cfqg_st(cfqg, i, j, st) {
 		*st = CFQ_RB_ROOT;
+		st->last_end_request = jiffies;
+	}
 	RB_CLEAR_NODE(&cfqg->rb_node);
 
 	/* Give preference to root group over other groups */