cfq-iosched: Remove prio_change logic for workload selection
[linux-2.6.git] / block / cfq-iosched.c
index d9bfa09..8df4fe5 100644 (file)
@@ -292,8 +292,7 @@ static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
 
 static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
                                            enum wl_prio_t prio,
-                                           enum wl_type_t type,
-                                           struct cfq_data *cfqd)
+                                           enum wl_type_t type)
 {
        if (!cfqg)
                return NULL;
@@ -1146,7 +1145,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 #endif
 
        service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
-                                               cfqq_type(cfqq), cfqd);
+                                               cfqq_type(cfqq));
        if (cfq_class_idle(cfqq)) {
                rb_key = CFQ_IDLE_DELAY;
                parent = rb_last(&service_tree->rb);
@@ -1609,7 +1608,7 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
 {
        struct cfq_rb_root *service_tree =
                service_tree_for(cfqd->serving_group, cfqd->serving_prio,
-                                       cfqd->serving_type, cfqd);
+                                       cfqd->serving_type);
 
        if (!cfqd->rq_queued)
                return NULL;
@@ -1956,8 +1955,7 @@ static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
 }
 
 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
-                               struct cfq_group *cfqg, enum wl_prio_t prio,
-                               bool prio_changed)
+                               struct cfq_group *cfqg, enum wl_prio_t prio)
 {
        struct cfq_queue *queue;
        int i;
@@ -1965,24 +1963,9 @@ static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
        unsigned long lowest_key = 0;
        enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
 
-       if (prio_changed) {
-               /*
-                * When priorities switched, we prefer starting
-                * from SYNC_NOIDLE (first choice), or just SYNC
-                * over ASYNC
-                */
-               if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
-                       return cur_best;
-               cur_best = SYNC_WORKLOAD;
-               if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
-                       return cur_best;
-
-               return ASYNC_WORKLOAD;
-       }
-
-       for (i = 0; i < 3; ++i) {
-               /* otherwise, select the one with lowest rb_key */
-               queue = cfq_rb_first(service_tree_for(cfqg, prio, i, cfqd));
+       for (i = 0; i <= SYNC_WORKLOAD; ++i) {
+               /* select the one with lowest rb_key */
+               queue = cfq_rb_first(service_tree_for(cfqg, prio, i));
                if (queue &&
                    (!key_valid || time_before(queue->rb_key, lowest_key))) {
                        lowest_key = queue->rb_key;
@@ -1996,8 +1979,6 @@ static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
 
 static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
 {
-       enum wl_prio_t previous_prio = cfqd->serving_prio;
-       bool prio_changed;
        unsigned slice;
        unsigned count;
        struct cfq_rb_root *st;
@@ -2025,24 +2006,19 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
         * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
         * expiration time
         */
-       prio_changed = (cfqd->serving_prio != previous_prio);
-       st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
-                               cfqd);
+       st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
        count = st->count;
 
        /*
-        * If priority didn't change, check workload expiration,
-        * and that we still have other queues ready
+        * check workload expiration, and that we still have other queues ready
         */
-       if (!prio_changed && count &&
-           !time_after(jiffies, cfqd->workload_expires))
+       if (count && !time_after(jiffies, cfqd->workload_expires))
                return;
 
        /* otherwise select new workload type */
        cfqd->serving_type =
-               cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio, prio_changed);
-       st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
-                               cfqd);
+               cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio);
+       st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
        count = st->count;
 
        /*