1 files changed, 24 insertions, 6 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 8830569542c4..3fc6be110c1d 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -378,6 +378,21 @@ CFQ_CFQQ_FNS(wait_busy);
                         &cfqg->service_trees[i][j]: NULL) \
 
 
+static inline bool iops_mode(struct cfq_data *cfqd)
+{
+        /*
+         * If we are not idling on queues and it is a NCQ drive, parallel
+         * execution of requests is on and measuring time is not possible
+         * in most of the cases until and unless we drive shallower queue
+         * depths and that becomes a performance bottleneck. In such cases
+         * switch to start providing fairness in terms of number of IOs.
+         */
+        if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
+                return true;
+        else
+                return false;
+}
+
 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
 {
         if (cfq_class_idle(cfqq))
@@ -906,7 +921,6 @@ static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
                         slice_used = cfqq->allocated_slice;
         }
 
-        cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u", slice_used);
         return slice_used;
 }
 
@@ -914,19 +928,21 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
                                 struct cfq_queue *cfqq)
 {
         struct cfq_rb_root *st = &cfqd->grp_service_tree;
-        unsigned int used_sl, charge_sl;
+        unsigned int used_sl, charge;
         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
                         - cfqg->service_tree_idle.count;
 
         BUG_ON(nr_sync < 0);
-        used_sl = charge_sl = cfq_cfqq_slice_usage(cfqq);
+        used_sl = charge = cfq_cfqq_slice_usage(cfqq);
 
-        if (!cfq_cfqq_sync(cfqq) && !nr_sync)
-                charge_sl = cfqq->allocated_slice;
+        if (iops_mode(cfqd))
+                charge = cfqq->slice_dispatch;
+        else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
+                charge = cfqq->allocated_slice;
 
         /* Can't update vdisktime while group is on service tree */
         cfq_rb_erase(&cfqg->rb_node, st);
-        cfqg->vdisktime += cfq_scale_slice(charge_sl, cfqg);
+        cfqg->vdisktime += cfq_scale_slice(charge, cfqg);
         __cfq_group_service_tree_add(st, cfqg);
 
         /* This group is being expired. Save the context */
@@ -940,6 +956,8 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
 
         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
                                         st->min_vdisktime);
+        cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u disp=%u charge=%u iops=%u",
+                        used_sl, cfqq->slice_dispatch, charge, iops_mode(cfqd));
         cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl);
         cfq_blkiocg_set_start_empty_time(&cfqg->blkg);
 }