From 435e30740f60199b722fa641f5cfcbed4e89f7f6 Mon Sep 17 00:00:00 2001
From: Jens Axboe <jaxboe@fusionio.com>
Date: Mon, 7 Mar 2011 09:40:21 +0100
Subject: [PATCH] --- yaml --- r: 242251 b: refs/heads/master c:
 b873c5d692d4d5453cceed18bb06c62bb1a73ac0 h: refs/heads/master i:   242249:
 6aeb5dae094c4c28902166dba7ee3de71e072769   242247:
 61a8abe42a0af21ea6873956ba36e94d234c62ac v: v3

---
 [refs]                    |  2 +-
 trunk/block/cfq-iosched.c | 35 +++++++++++++++++++++++++++--------
 2 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/[refs] b/[refs]
index 720be9b05d80..7f0d3457777e 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: e83a46bbb1d4c03defd733a64b727632a40059ad
+refs/heads/master: b873c5d692d4d5453cceed18bb06c62bb1a73ac0
diff --git a/trunk/block/cfq-iosched.c b/trunk/block/cfq-iosched.c
index 89dc745c7d94..9697053f80bc 100644
--- a/trunk/block/cfq-iosched.c
+++ b/trunk/block/cfq-iosched.c
@@ -237,6 +237,7 @@ struct cfq_data {
 	struct rb_root prio_trees[CFQ_PRIO_LISTS];
 
 	unsigned int busy_queues;
+	unsigned int busy_sync_queues;
 
 	int rq_in_driver;
 	int rq_in_flight[2];
@@ -556,15 +557,13 @@ static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
 
 static void update_min_vdisktime(struct cfq_rb_root *st)
 {
-	u64 vdisktime = st->min_vdisktime;
 	struct cfq_group *cfqg;
 
 	if (st->left) {
 		cfqg = rb_entry_cfqg(st->left);
-		vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
+		st->min_vdisktime = max_vdisktime(st->min_vdisktime,
+						  cfqg->vdisktime);
 	}
-
-	st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
 }
 
 /*
@@ -1344,6 +1343,8 @@ static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 	BUG_ON(cfq_cfqq_on_rr(cfqq));
 	cfq_mark_cfqq_on_rr(cfqq);
 	cfqd->busy_queues++;
+	if (cfq_cfqq_sync(cfqq))
+		cfqd->busy_sync_queues++;
 
 	cfq_resort_rr_list(cfqd, cfqq);
 }
@@ -1370,6 +1371,8 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 	cfq_group_service_tree_del(cfqd, cfqq->cfqg);
 	BUG_ON(!cfqd->busy_queues);
 	cfqd->busy_queues--;
+	if (cfq_cfqq_sync(cfqq))
+		cfqd->busy_sync_queues--;
 }
 
 /*
@@ -2377,22 +2380,39 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 	 * Does this cfqq already have too much IO in flight?
 	 */
 	if (cfqq->dispatched >= max_dispatch) {
+		bool promote_sync = false;
 		/*
 		 * idle queue must always only have a single IO in flight
 		 */
 		if (cfq_class_idle(cfqq))
 			return false;
 
+		/*
+		 * If there is only one sync queue, and its think time is
+		 * small, we can ignore async queue here and give the sync
+		 * queue no dispatch limit. The reason is a sync queue can
+		 * preempt async queue, limiting the sync queue doesn't make
+		 * sense. This is useful for aiostress test.
+		 */
+		if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1) {
+			struct cfq_io_context *cic = RQ_CIC(cfqq->next_rq);
+
+			if (sample_valid(cic->ttime_samples) &&
+				cic->ttime_mean < cfqd->cfq_slice_idle)
+				promote_sync = true;
+		}
+
 		/*
 		 * We have other queues, don't allow more IO from this one
 		 */
-		if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq))
+		if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
+				!promote_sync)
 			return false;
 
 		/*
 		 * Sole queue user, no limit
 		 */
-		if (cfqd->busy_queues == 1)
+		if (cfqd->busy_queues == 1 || promote_sync)
 			max_dispatch = -1;
 		else
 			/*
@@ -3675,12 +3695,11 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 
 	cfqq->allocated[rw]++;
 
-	spin_unlock_irqrestore(q->queue_lock, flags);
-
 	cfqq->ref++;
 	rq->elevator_private[0] = cic;
 	rq->elevator_private[1] = cfqq;
 	rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
+	spin_unlock_irqrestore(q->queue_lock, flags);
 	return 0;
 
 queue_fail: