1 files changed, 148 insertions, 94 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 1ca813b16e78..069a61017c02 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -173,6 +173,7 @@ struct cfq_data {
         unsigned int cfq_slice[2];
         unsigned int cfq_slice_async_rq;
         unsigned int cfq_slice_idle;
+        unsigned int cfq_latency;
 
         struct list_head cic_list;
 
@@ -180,6 +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 {
@@ -227,7 +230,7 @@ CFQ_CFQQ_FNS(coop);
         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
 
 static void cfq_dispatch_insert(struct request_queue *, struct request *);
-static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
+static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
                                        struct io_context *, gfp_t);
 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
                                                 struct io_context *);
@@ -238,27 +241,24 @@ static inline int rq_in_driver(struct cfq_data *cfqd)
 }
 
 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
-                                            int is_sync)
+                                            bool is_sync)
 {
-        return cic->cfqq[!!is_sync];
+        return cic->cfqq[is_sync];
 }
 
 static inline void cic_set_cfqq(struct cfq_io_context *cic,
-                                struct cfq_queue *cfqq, int is_sync)
+                                struct cfq_queue *cfqq, bool is_sync)
 {
-        cic->cfqq[!!is_sync] = cfqq;
+        cic->cfqq[is_sync] = cfqq;
 }
 
 /*
  * We regard a request as SYNC, if it's either a read or has the SYNC bit
  * set (in which case it could also be direct WRITE).
  */
-static inline int cfq_bio_sync(struct bio *bio)
+static inline bool cfq_bio_sync(struct bio *bio)
 {
-        if (bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO))
-                return 1;
-
-        return 0;
+        return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
 }
 
 /*
@@ -285,7 +285,7 @@ static int cfq_queue_empty(struct request_queue *q)
  * if a queue is marked sync and has sync io queued. A sync queue with async
  * io only, should not get full sync slice length.
  */
-static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync,
+static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
                                  unsigned short prio)
 {
         const int base_slice = cfqd->cfq_slice[sync];
@@ -313,7 +313,7 @@ cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
  * isn't valid until the first request from the dispatch is activated
  * and the slice time set.
  */
-static inline int cfq_slice_used(struct cfq_queue *cfqq)
+static inline bool cfq_slice_used(struct cfq_queue *cfqq)
 {
         if (cfq_cfqq_slice_new(cfqq))
                 return 0;
@@ -488,7 +488,7 @@ static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
  * we will service the queues.
  */
 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
-                                 int add_front)
+                                 bool add_front)
 {
         struct rb_node **p, *parent;
         struct cfq_queue *__cfqq;
@@ -504,11 +504,20 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                 } else
                         rb_key += jiffies;
         } else if (!add_front) {
+                /*
+                 * Get our rb key offset. Subtract any residual slice
+                 * value carried from last service. A negative resid
+                 * count indicates slice overrun, and this should position
+                 * the next service time further away in the tree.
+                 */
                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
-                rb_key += cfqq->slice_resid;
+                rb_key -= cfqq->slice_resid;
                 cfqq->slice_resid = 0;
-        } else
-                rb_key = 0;
+        } else {
+                rb_key = -HZ;
+                __cfqq = cfq_rb_first(&cfqd->service_tree);
+                rb_key += __cfqq ? __cfqq->rb_key : jiffies;
+        }
 
         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
                 /*
@@ -542,7 +551,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                         n = &(*p)->rb_left;
                 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
                         n = &(*p)->rb_right;
-                else if (rb_key < __cfqq->rb_key)
+                else if (time_before(rb_key, __cfqq->rb_key))
                         n = &(*p)->rb_left;
                 else
                         n = &(*p)->rb_right;
@@ -822,8 +831,10 @@ cfq_merged_requests(struct request_queue *q, struct request *rq,
          * reposition in fifo if next is older than rq
          */
         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
-            time_before(next->start_time, rq->start_time))
+            time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
                 list_move(&rq->queuelist, &next->queuelist);
+                rq_set_fifo_time(rq, rq_fifo_time(next));
+        }
 
         cfq_remove_request(next);
 }
@@ -839,7 +850,7 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
          * Disallow merge of a sync bio into an async request.
          */
         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
-                return 0;
+                return false;
 
         /*
          * Lookup the cfqq that this bio will be queued with. Allow
@@ -847,13 +858,10 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
          */
         cic = cfq_cic_lookup(cfqd, current->io_context);
         if (!cic)
-                return 0;
+                return false;
 
         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
-        if (cfqq == RQ_CFQQ(rq))
-                return 1;
-
-        return 0;
+        return cfqq == RQ_CFQQ(rq);
 }
 
 static void __cfq_set_active_queue(struct cfq_data *cfqd,
@@ -881,7 +889,7 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
  */
 static void
 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
-                    int timed_out)
+                    bool timed_out)
 {
         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
 
@@ -909,7 +917,7 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         }
 }
 
-static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
+static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
 {
         struct cfq_queue *cfqq = cfqd->active_queue;
 
@@ -1021,7 +1029,7 @@ static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
  */
 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
                                               struct cfq_queue *cur_cfqq,
-                                              int probe)
+                                              bool probe)
 {
         struct cfq_queue *cfqq;
 
@@ -1085,6 +1093,15 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
         if (!cic || !atomic_read(&cic->ioc->nr_tasks))
                 return;
 
+        /*
+         * If our average think time is larger than the remaining time
+         * slice, then don't idle. This avoids overrunning the allotted
+         * time slice.
+         */
+        if (sample_valid(cic->ttime_samples) &&
+            (cfqq->slice_end - jiffies < cic->ttime_mean))
+                return;
+
         cfq_mark_cfqq_wait_request(cfqq);
 
         /*
@@ -1124,9 +1141,7 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
  */
 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
 {
-        struct cfq_data *cfqd = cfqq->cfqd;
-        struct request *rq;
-        int fifo;
+        struct request *rq = NULL;
 
         if (cfq_cfqq_fifo_expire(cfqq))
                 return NULL;
@@ -1136,13 +1151,11 @@ static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
         if (list_empty(&cfqq->fifo))
                 return NULL;
 
-        fifo = cfq_cfqq_sync(cfqq);
         rq = rq_entry_fifo(cfqq->fifo.next);
-
-        if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
+        if (time_before(jiffies, rq_fifo_time(rq)))
                 rq = NULL;
 
-        cfq_log_cfqq(cfqd, cfqq, "fifo=%p", rq);
+        cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
         return rq;
 }
 
@@ -1243,16 +1256,83 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd)
         return dispatched;
 }
 
+static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+        unsigned int max_dispatch;
+
+        /*
+         * Drain async requests before we start sync IO
+         */
+        if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
+                return false;
+
+        /*
+         * If this is an async queue and we have sync IO in flight, let it wait
+         */
+        if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
+                return false;
+
+        max_dispatch = cfqd->cfq_quantum;
+        if (cfq_class_idle(cfqq))
+                max_dispatch = 1;
+
+        /*
+         * Does this cfqq already have too much IO in flight?
+         */
+        if (cfqq->dispatched >= max_dispatch) {
+                /*
+                 * idle queue must always only have a single IO in flight
+                 */
+                if (cfq_class_idle(cfqq))
+                        return false;
+
+                /*
+                 * We have other queues, don't allow more IO from this one
+                 */
+                if (cfqd->busy_queues > 1)
+                        return false;
+
+                /*
+                 * Sole queue user, allow bigger slice
+                 */
+                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_latency) {
+                unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
+                unsigned int depth;
+
+                depth = last_sync / cfqd->cfq_slice[1];
+                if (!depth && !cfqq->dispatched)
+                        depth = 1;
+                if (depth < max_dispatch)
+                        max_dispatch = depth;
+        }
+
+        /*
+         * If we're below the current max, allow a dispatch
+         */
+        return cfqq->dispatched < max_dispatch;
+}
+
 /*
  * Dispatch a request from cfqq, moving them to the request queue
  * dispatch list.
  */
-static void cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
         struct request *rq;
 
         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
 
+        if (!cfq_may_dispatch(cfqd, cfqq))
+                return false;
+
         /*
          * follow expired path, else get first next available
          */
@@ -1271,6 +1351,8 @@ static void cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
                 atomic_long_inc(&cic->ioc->refcount);
                 cfqd->active_cic = cic;
         }
+
+        return true;
 }
 
 /*
@@ -1281,7 +1363,6 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
         struct cfq_queue *cfqq;
-        unsigned int max_dispatch;
 
         if (!cfqd->busy_queues)
                 return 0;
@@ -1294,48 +1375,11 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
                 return 0;
 
         /*
-         * Drain async requests before we start sync IO
+         * Dispatch a request from this cfqq, if it is allowed
          */
-        if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
+        if (!cfq_dispatch_request(cfqd, cfqq))
                 return 0;
 
-        /*
-         * If this is an async queue and we have sync IO in flight, let it wait
-         */
-        if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
-                return 0;
-
-        max_dispatch = cfqd->cfq_quantum;
-        if (cfq_class_idle(cfqq))
-                max_dispatch = 1;
-
-        /*
-         * Does this cfqq already have too much IO in flight?
-         */
-        if (cfqq->dispatched >= max_dispatch) {
-                /*
-                 * idle queue must always only have a single IO in flight
-                 */
-                if (cfq_class_idle(cfqq))
-                        return 0;
-
-                /*
-                 * We have other queues, don't allow more IO from this one
-                 */
-                if (cfqd->busy_queues > 1)
-                        return 0;
-
-                /*
-                 * we are the only queue, allow up to 4 times of 'quantum'
-                 */
-                if (cfqq->dispatched >= 4 * max_dispatch)
-                        return 0;
-        }
-
-        /*
-         * Dispatch a request from this cfqq
-         */
-        cfq_dispatch_request(cfqd, cfqq);
         cfqq->slice_dispatch++;
         cfq_clear_cfqq_must_dispatch(cfqq);
 
@@ -1635,7 +1679,7 @@ static void cfq_ioc_set_ioprio(struct io_context *ioc)
 }
 
 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
-                          pid_t pid, int is_sync)
+                          pid_t pid, bool is_sync)
 {
         RB_CLEAR_NODE(&cfqq->rb_node);
         RB_CLEAR_NODE(&cfqq->p_node);
@@ -1655,7 +1699,7 @@ static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 }
 
 static struct cfq_queue *
-cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
+cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
                      struct io_context *ioc, gfp_t gfp_mask)
 {
         struct cfq_queue *cfqq, *new_cfqq = NULL;
@@ -1719,7 +1763,7 @@ cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
 }
 
 static struct cfq_queue *
-cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
+cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
               gfp_t gfp_mask)
 {
         const int ioprio = task_ioprio(ioc);
@@ -1951,10 +1995,13 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
 
         if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
-            (cfqd->hw_tag && CIC_SEEKY(cic)))
+            (!cfqd->cfq_latency && cfqd->hw_tag && CIC_SEEKY(cic)))
                 enable_idle = 0;
         else if (sample_valid(cic->ttime_samples)) {
-                if (cic->ttime_mean > cfqd->cfq_slice_idle)
+                unsigned int slice_idle = cfqd->cfq_slice_idle;
+                if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
+                        slice_idle = msecs_to_jiffies(CFQ_MIN_TT);
+                if (cic->ttime_mean > slice_idle)
                         enable_idle = 0;
                 else
                         enable_idle = 1;
@@ -1973,7 +2020,7 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
  * Check if new_cfqq should preempt the currently active queue. Return 0 for
  * no or if we aren't sure, a 1 will cause a preempt.
  */
-static int
+static bool
 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
                    struct request *rq)
 {
@@ -1981,48 +2028,48 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
 
         cfqq = cfqd->active_queue;
         if (!cfqq)
-                return 0;
+                return false;
 
         if (cfq_slice_used(cfqq))
-                return 1;
+                return true;
 
         if (cfq_class_idle(new_cfqq))
-                return 0;
+                return false;
 
         if (cfq_class_idle(cfqq))
-                return 1;
+                return true;
 
         /*
          * if the new request is sync, but the currently running queue is
          * not, let the sync request have priority.
          */
         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
-                return 1;
+                return true;
 
         /*
          * So both queues are sync. Let the new request get disk time if
          * it's a metadata request and the current queue is doing regular IO.
          */
         if (rq_is_meta(rq) && !cfqq->meta_pending)
-                return 1;
+                return false;
 
         /*
          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
          */
         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
-                return 1;
+                return true;
 
         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
-                return 0;
+                return false;
 
         /*
          * if this request is as-good as one we would expect from the
          * current cfqq, let it preempt
          */
         if (cfq_rq_close(cfqd, rq))
-                return 1;
+                return true;
 
-        return 0;
+        return false;
 }
 
 /*
@@ -2107,6 +2154,7 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
 
         cfq_add_rq_rb(rq);
 
+        rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
         list_add_tail(&rq->queuelist, &cfqq->fifo);
 
         cfq_rq_enqueued(cfqd, cfqq, rq);
@@ -2157,8 +2205,10 @@ 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,
@@ -2284,7 +2334,7 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
         struct cfq_data *cfqd = q->elevator->elevator_data;
         struct cfq_io_context *cic;
         const int rw = rq_data_dir(rq);
-        const int is_sync = rq_is_sync(rq);
+        const bool is_sync = rq_is_sync(rq);
         struct cfq_queue *cfqq;
         unsigned long flags;
 
@@ -2480,8 +2530,9 @@ static void *cfq_init_queue(struct request_queue *q)
         cfqd->cfq_slice[1] = cfq_slice_sync;
         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
         cfqd->cfq_slice_idle = cfq_slice_idle;
+        cfqd->cfq_latency = 1;
         cfqd->hw_tag = 1;
-
+        cfqd->last_end_sync_rq = jiffies;
         return cfqd;
 }
 
@@ -2549,6 +2600,7 @@ SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
+SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
 #undef SHOW_FUNCTION
 
 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
@@ -2580,6 +2632,7 @@ STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
                 UINT_MAX, 0);
+STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
 #undef STORE_FUNCTION
 
 #define CFQ_ATTR(name) \
@@ -2595,6 +2648,7 @@ static struct elv_fs_entry cfq_attrs[] = {
         CFQ_ATTR(slice_async),
         CFQ_ATTR(slice_async_rq),
         CFQ_ATTR(slice_idle),
+        CFQ_ATTR(low_latency),
         __ATTR_NULL
 };