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Commit 5ad531db authored by Jens Axboe's avatar Jens Axboe
Browse files

cfq-iosched: drain device queue before switching to a sync queue 



To lessen the impact of async IO on sync IO, let the device drain of
any async IO in progress when switching to a sync cfqq that has idling
enabled.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent da6c5c72

block/cfq-iosched.c

+25 −13
Original line number Diff line number Diff line
@@ -140,7 +140,7 @@ struct cfq_data { 
	 */

	unsigned int busy_rt_queues;



	int rq_in_driver;

	int rq_in_driver[2];

	int sync_flight;



	/*
@@ -239,6 +239,11 @@ static struct cfq_queue *cfq_get_queue(struct cfq_data *, int, 
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,

					    int is_sync)

{
@@ -760,9 +765,9 @@ static void cfq_activate_request(struct request_queue *q, struct request *rq) 
{

	struct cfq_data *cfqd = q->elevator->elevator_data;



	cfqd->rq_in_driver++;

	cfqd->rq_in_driver[rq_is_sync(rq)]++;

	cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",

						cfqd->rq_in_driver);

						rq_in_driver(cfqd));



	cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);

}
@@ -770,11 +775,12 @@ 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);

	cfqd->rq_in_driver--;

	WARN_ON(!cfqd->rq_in_driver[sync]);

	cfqd->rq_in_driver[sync]--;

	cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",

						cfqd->rq_in_driver);

						rq_in_driver(cfqd));

}



static void cfq_remove_request(struct request *rq)
@@ -1080,7 +1086,7 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd) 
	/*

	 * still requests with the driver, don't idle

	 */

	if (cfqd->rq_in_driver)

	if (rq_in_driver(cfqd))

		return;



	/*
@@ -1311,6 +1317,12 @@ static int cfq_dispatch_requests(struct request_queue *q, int force) 
	if (!cfqq)

		return 0;



	/*

	 * Drain async requests before we start sync IO

	 */

	if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])

		return 0;



	/*

	 * If this is an async queue and we have sync IO in flight, let it wait

	 */
@@ -2130,11 +2142,11 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq) 
 */

static void cfq_update_hw_tag(struct cfq_data *cfqd)

{

	if (cfqd->rq_in_driver > cfqd->rq_in_driver_peak)

		cfqd->rq_in_driver_peak = cfqd->rq_in_driver;

	if (rq_in_driver(cfqd) > cfqd->rq_in_driver_peak)

		cfqd->rq_in_driver_peak = rq_in_driver(cfqd);



	if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&

	    cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)

	    rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)

		return;



	if (cfqd->hw_tag_samples++ < 50)
@@ -2161,9 +2173,9 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq) 


	cfq_update_hw_tag(cfqd);



	WARN_ON(!cfqd->rq_in_driver);

	WARN_ON(!cfqd->rq_in_driver[sync]);

	WARN_ON(!cfqq->dispatched);

	cfqd->rq_in_driver--;

	cfqd->rq_in_driver[sync]--;

	cfqq->dispatched--;



	if (cfq_cfqq_sync(cfqq))
@@ -2197,7 +2209,7 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq) 
			cfq_arm_slice_timer(cfqd);

	}



	if (!cfqd->rq_in_driver)

	if (!rq_in_driver(cfqd))

		cfq_schedule_dispatch(cfqd);

}