cfq-iosched: requests "in flight" vs "in driver" clarification
Corrado Zoccolo [Sun, 28 Feb 2010 18:45:05 +0000 (19:45 +0100)]
Counters for requests "in flight" and "in driver" are used asymmetrically
in cfq_may_dispatch, and have slightly different meaning.
We split the rq_in_flight counter (was sync_flight) to count both sync
and async requests, in order to use this one, which is more accurate in
some corner cases.
The rq_in_driver counter is coalesced, since individual sync/async counts
are not used any more.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/cfq-iosched.c

index 423aee3..f27e535 100644 (file)
@@ -222,8 +222,8 @@ struct cfq_data {
 
        unsigned int busy_queues;
 
-       int rq_in_driver[2];
-       int sync_flight;
+       int rq_in_driver;
+       int rq_in_flight[2];
 
        /*
         * queue-depth detection
@@ -416,11 +416,6 @@ static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
                                                struct io_context *);
 
-static inline int rq_in_driver(struct cfq_data *cfqd)
-{
-       return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
-}
-
 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
                                            bool is_sync)
 {
@@ -1414,9 +1409,9 @@ static void cfq_activate_request(struct request_queue *q, struct request *rq)
 {
        struct cfq_data *cfqd = q->elevator->elevator_data;
 
-       cfqd->rq_in_driver[rq_is_sync(rq)]++;
+       cfqd->rq_in_driver++;
        cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
-                                               rq_in_driver(cfqd));
+                                               cfqd->rq_in_driver);
 
        cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
 }
@@ -1424,12 +1419,11 @@ static void cfq_activate_request(struct request_queue *q, struct request *rq)
 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
 {
        struct cfq_data *cfqd = q->elevator->elevator_data;
-       const int sync = rq_is_sync(rq);
 
-       WARN_ON(!cfqd->rq_in_driver[sync]);
-       cfqd->rq_in_driver[sync]--;
+       WARN_ON(!cfqd->rq_in_driver);
+       cfqd->rq_in_driver--;
        cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
-                                               rq_in_driver(cfqd));
+                                               cfqd->rq_in_driver);
 }
 
 static void cfq_remove_request(struct request *rq)
@@ -1863,8 +1857,7 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
        cfqq->dispatched++;
        elv_dispatch_sort(q, rq);
 
-       if (cfq_cfqq_sync(cfqq))
-               cfqd->sync_flight++;
+       cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
        cfqq->nr_sectors += blk_rq_sectors(rq);
 }
 
@@ -2211,13 +2204,13 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
        /*
         * Drain async requests before we start sync IO
         */
-       if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
+       if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[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))
+       if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
                return false;
 
        max_dispatch = cfqd->cfq_quantum;
@@ -3189,14 +3182,14 @@ static void cfq_update_hw_tag(struct cfq_data *cfqd)
 {
        struct cfq_queue *cfqq = cfqd->active_queue;
 
-       if (rq_in_driver(cfqd) > cfqd->hw_tag_est_depth)
-               cfqd->hw_tag_est_depth = rq_in_driver(cfqd);
+       if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
+               cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
 
        if (cfqd->hw_tag == 1)
                return;
 
        if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
-           rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
+           cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
                return;
 
        /*
@@ -3206,7 +3199,7 @@ static void cfq_update_hw_tag(struct cfq_data *cfqd)
         */
        if (cfqq && cfq_cfqq_idle_window(cfqq) &&
            cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
-           CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
+           CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
                return;
 
        if (cfqd->hw_tag_samples++ < 50)
@@ -3259,13 +3252,12 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
 
        cfq_update_hw_tag(cfqd);
 
-       WARN_ON(!cfqd->rq_in_driver[sync]);
+       WARN_ON(!cfqd->rq_in_driver);
        WARN_ON(!cfqq->dispatched);
-       cfqd->rq_in_driver[sync]--;
+       cfqd->rq_in_driver--;
        cfqq->dispatched--;
 
-       if (cfq_cfqq_sync(cfqq))
-               cfqd->sync_flight--;
+       cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
 
        if (sync) {
                RQ_CIC(rq)->last_end_request = now;
@@ -3319,7 +3311,7 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
                }
        }
 
-       if (!rq_in_driver(cfqd))
+       if (!cfqd->rq_in_driver)
                cfq_schedule_dispatch(cfqd);
 }