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Commit 99f9628a authored by Jens Axboe's avatar Jens Axboe Committed by Jens Axboe
Browse files

[PATCH] cfq-iosched: use last service point as the fairness criteria 



Right now we use slice_start, which gives async queues an unfair
advantage. Chance that to service_last, and base the resorter
on that.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent b0b8d749

block/cfq-iosched.c

+34 −14
Original line number Original line Diff line number Diff line
@@ -146,9 +146,9 @@ struct cfq_queue { 
	/* fifo list of requests in sort_list */

	/* fifo list of requests in sort_list */

	struct list_head fifo;

	struct list_head fifo;





	unsigned long slice_start;

	unsigned long slice_end;

	unsigned long slice_end;

	unsigned long slice_left;

	unsigned long slice_left;

	unsigned long service_last;





	/* number of requests that are on the dispatch list */

	/* number of requests that are on the dispatch list */

	int on_dispatch[2];

	int on_dispatch[2];
@@ -355,7 +355,8 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)

static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)

{

{

	struct cfq_data *cfqd = cfqq->cfqd;

	struct cfq_data *cfqd = cfqq->cfqd;

	struct list_head *list;

	struct list_head *list, *n;

	struct cfq_queue *__cfqq;





	/*

	/*

	 * Resorting requires the cfqq to be on the RR list already.

	 * Resorting requires the cfqq to be on the RR list already.
@@ -383,15 +384,13 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted) 
			list = &cfqd->rr_list[cfqq->ioprio];

			list = &cfqd->rr_list[cfqq->ioprio];

	}

	}





	if (preempted || cfq_cfqq_queue_new(cfqq)) {

		/*

		/*

	 * If this queue was preempted or is new (never been serviced), let

		 * If this queue was preempted or is new (never been serviced),

	 * it be added first for fairness but beind other new queues.

		 * let it be added first for fairness but beind other new

	 * Otherwise, just add to the back  of the list.

		 * queues.

		 */

		 */

	if (preempted || cfq_cfqq_queue_new(cfqq)) {

		n = list;

		struct list_head *n = list;

		struct cfq_queue *__cfqq;



		while (n->next != list) {

		while (n->next != list) {

			__cfqq = list_entry_cfqq(n->next);

			__cfqq = list_entry_cfqq(n->next);

			if (!cfq_cfqq_queue_new(__cfqq))

			if (!cfq_cfqq_queue_new(__cfqq))
@@ -399,11 +398,32 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted) 




			n = n->next;

			n = n->next;

		}

		}

		list_add_tail(&cfqq->cfq_list, n);

	} else if (!cfq_cfqq_class_sync(cfqq)) {

		/*

		 * async queue always goes to the end. this wont be overly

		 * unfair to writes, as the sort of the sync queue wont be

		 * allowed to pass the async queue again.

		 */

		list_add_tail(&cfqq->cfq_list, list);

	} else {

		/*

		 * sort by last service, but don't cross a new or async

		 * queue. we don't cross a new queue because it hasn't been

		 * service before, and we don't cross an async queue because

		 * it gets added to the end on expire.

		 */

		n = list;

		while ((n = n->prev) != list) {

			struct cfq_queue *__cfqq = list_entry_cfqq(n);





		list = n;

			if (!cfq_cfqq_class_sync(cfqq) || !__cfqq->service_last)

				break;

			if (time_before(__cfqq->service_last, cfqq->service_last))

				break;

		}

		list_add(&cfqq->cfq_list, n);

	}

	}



	list_add_tail(&cfqq->cfq_list, list);

}

}





/*

/*
@@ -608,7 +628,6 @@ __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 
		 */

		 */

		del_timer(&cfqd->idle_class_timer);

		del_timer(&cfqd->idle_class_timer);





		cfqq->slice_start = jiffies;

		cfqq->slice_end = 0;

		cfqq->slice_end = 0;

		cfqq->slice_left = 0;

		cfqq->slice_left = 0;

		cfq_clear_cfqq_must_alloc_slice(cfqq);

		cfq_clear_cfqq_must_alloc_slice(cfqq);
@@ -1688,6 +1707,7 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq) 
	WARN_ON(!cfqq->on_dispatch[sync]);

	WARN_ON(!cfqq->on_dispatch[sync]);

	cfqd->rq_in_driver--;

	cfqd->rq_in_driver--;

	cfqq->on_dispatch[sync]--;

	cfqq->on_dispatch[sync]--;

	cfqq->service_last = now;





	if (!cfq_class_idle(cfqq))

	if (!cfq_class_idle(cfqq))

		cfqd->last_end_request = now;

		cfqd->last_end_request = now;