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Commit 53c583d2 authored by Corrado Zoccolo's avatar Corrado Zoccolo Committed by Jens Axboe
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cfq-iosched: requests "in flight" vs "in driver" clarification 



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: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 87c3a922

block/cfq-iosched.c

+18 −26
Original line number Diff line number Diff line
@@ -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);

}