3 files changed, 48 insertions, 20 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index ddaaea4fdffc..a8c7fbe52e24 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2492,6 +2492,14 @@ int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
 }
 EXPORT_SYMBOL(kblockd_schedule_work);
 
+int kblockd_schedule_delayed_work(struct request_queue *q,
+                                  struct delayed_work *work,
+                                  unsigned long delay)
+{
+        return queue_delayed_work(kblockd_workqueue, work, delay);
+}
+EXPORT_SYMBOL(kblockd_schedule_delayed_work);
+
 int __init blk_dev_init(void)
 {
         BUILD_BUG_ON(__REQ_NR_BITS > 8 *
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 70b48ea0e3e9..fce8a749f4be 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -150,7 +150,7 @@ struct cfq_data {
          * idle window management
          */
         struct timer_list idle_slice_timer;
-        struct work_struct unplug_work;
+        struct delayed_work unplug_work;
 
         struct cfq_queue *active_queue;
         struct cfq_io_context *active_cic;
@@ -268,11 +268,13 @@ static inline int cfq_bio_sync(struct bio *bio)
  * scheduler run of queue, if there are requests pending and no one in the
  * driver that will restart queueing
  */
-static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
+static inline void cfq_schedule_dispatch(struct cfq_data *cfqd,
+                                         unsigned long delay)
 {
         if (cfqd->busy_queues) {
                 cfq_log(cfqd, "schedule dispatch");
-                kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
+                kblockd_schedule_delayed_work(cfqd->queue, &cfqd->unplug_work,
+                                                delay);
         }
 }
 
@@ -1316,8 +1318,6 @@ 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
                  */
@@ -1331,20 +1331,36 @@ 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.
+                 * Sole queue user, allow bigger slice
                  */
-                if (cfqd->cfq_desktop && !cfq_cfqq_sync(cfqq)
-                    && time_before(jiffies, load_at))
-                        return 0;
+                max_dispatch *= 4;
+        }
+
+        /*
+         * Async queues must wait a bit before being allowed dispatch.
+         * We also ramp up the dispatch depth gradually for async IO,
+         * based on the last sync IO we serviced
+         */
+        if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_desktop) {
+                unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
+                unsigned int depth;
 
                 /*
-                 * we are the only queue, allow up to 4 times of 'quantum'
+                 * must wait a bit longer
                  */
-                if (cfqq->dispatched >= 4 * max_dispatch)
+                if (last_sync < cfq_slice_sync) {
+                        cfq_schedule_dispatch(cfqd, cfq_slice_sync - last_sync);
                         return 0;
+                }
+
+                depth = last_sync / cfq_slice_sync;
+                if (depth < max_dispatch)
+                        max_dispatch = depth;
         }
 
+        if (cfqq->dispatched >= max_dispatch)
+                return 0;
+
         /*
          * Dispatch a request from this cfqq
          */
@@ -1389,7 +1405,7 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
 
         if (unlikely(cfqd->active_queue == cfqq)) {
                 __cfq_slice_expired(cfqd, cfqq, 0);
-                cfq_schedule_dispatch(cfqd);
+                cfq_schedule_dispatch(cfqd, 0);
         }
 
         kmem_cache_free(cfq_pool, cfqq);
@@ -1484,7 +1500,7 @@ static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
         if (unlikely(cfqq == cfqd->active_queue)) {
                 __cfq_slice_expired(cfqd, cfqq, 0);
-                cfq_schedule_dispatch(cfqd);
+                cfq_schedule_dispatch(cfqd, 0);
         }
 
         cfq_put_queue(cfqq);
@@ -2201,7 +2217,7 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
         }
 
         if (!rq_in_driver(cfqd))
-                cfq_schedule_dispatch(cfqd);
+                cfq_schedule_dispatch(cfqd, 0);
 }
 
 /*
@@ -2331,7 +2347,7 @@ queue_fail:
         if (cic)
                 put_io_context(cic->ioc);
 
-        cfq_schedule_dispatch(cfqd);
+        cfq_schedule_dispatch(cfqd, 0);
         spin_unlock_irqrestore(q->queue_lock, flags);
         cfq_log(cfqd, "set_request fail");
         return 1;
@@ -2340,7 +2356,7 @@ queue_fail:
 static void cfq_kick_queue(struct work_struct *work)
 {
         struct cfq_data *cfqd =
-                container_of(work, struct cfq_data, unplug_work);
+                container_of(work, struct cfq_data, unplug_work.work);
         struct request_queue *q = cfqd->queue;
 
         spin_lock_irq(q->queue_lock);
@@ -2394,7 +2410,7 @@ static void cfq_idle_slice_timer(unsigned long data)
 expire:
         cfq_slice_expired(cfqd, timed_out);
 out_kick:
-        cfq_schedule_dispatch(cfqd);
+        cfq_schedule_dispatch(cfqd, 0);
 out_cont:
         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
 }
@@ -2402,7 +2418,7 @@ out_cont:
 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
 {
         del_timer_sync(&cfqd->idle_slice_timer);
-        cancel_work_sync(&cfqd->unplug_work);
+        cancel_delayed_work_sync(&cfqd->unplug_work);
 }
 
 static void cfq_put_async_queues(struct cfq_data *cfqd)
@@ -2484,7 +2500,7 @@ static void *cfq_init_queue(struct request_queue *q)
         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
 
-        INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
+        INIT_DELAYED_WORK(&cfqd->unplug_work, cfq_kick_queue);
 
         cfqd->cfq_quantum = cfq_quantum;
         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1a03b715dfad..a7323930d2ba 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1147,7 +1147,11 @@ static inline void put_dev_sector(Sector p)
 }
 
 struct work_struct;
+struct delayed_work;
 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work);
+int kblockd_schedule_delayed_work(struct request_queue *q,
+                                        struct delayed_work *work,
+                                        unsigned long delay);
 
 #define MODULE_ALIAS_BLOCKDEV(major,minor) \
         MODULE_ALIAS("block-major-" __stringify(major) "-" __stringify(minor))