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Commit c5b680f3 authored by Jens Axboe's avatar Jens Axboe Committed by Jens Axboe
Browse files

cfq-iosched: account for slice over/under time 



If a slice uses less than it is entitled to (or perhaps more), include
that in the decision on how much time to give it the next time it
gets serviced.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 44f7c160

block/cfq-iosched.c

+12 −20
Original line number Diff line number Diff line
@@ -147,8 +147,8 @@ struct cfq_queue { 
	struct list_head fifo;



	unsigned long slice_end;

	unsigned long slice_left;

	unsigned long service_last;

	long slice_resid;



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

	int on_dispatch[2];
@@ -251,6 +251,14 @@ static inline void 
cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)

{

	cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;

	cfqq->slice_end += cfqq->slice_resid;



	/*

	 * Don't carry over residual for more than one slice, we only want

	 * to slightly correct the fairness. Carrying over forever would

	 * easily introduce oscillations.

	 */

	cfqq->slice_resid = 0;

}



/*
@@ -667,7 +675,6 @@ __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 
		del_timer(&cfqd->idle_class_timer);



		cfqq->slice_end = 0;

		cfqq->slice_left = 0;

		cfq_clear_cfqq_must_alloc_slice(cfqq);

		cfq_clear_cfqq_fifo_expire(cfqq);

		cfq_mark_cfqq_slice_new(cfqq);
@@ -683,8 +690,6 @@ static void 
__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,

		    int preempted)

{

	unsigned long now = jiffies;



	if (cfq_cfqq_wait_request(cfqq))

		del_timer(&cfqd->idle_slice_timer);
@@ -699,10 +704,8 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	 * store what was left of this slice, if the queue idled out

	 * or was preempted

	 */

	if (cfq_slice_used(cfqq))

		cfqq->slice_left = cfqq->slice_end - now;

	else

		cfqq->slice_left = 0;

	if (!cfq_cfqq_slice_new(cfqq))

		cfqq->slice_resid = cfqq->slice_end - jiffies;



	cfq_resort_rr_list(cfqq, preempted);
@@ -1364,10 +1367,7 @@ cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, 
		hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);

		atomic_set(&cfqq->ref, 0);

		cfqq->cfqd = cfqd;

		/*

		 * set ->slice_left to allow preemption for a new process

		 */

		cfqq->slice_left = 2 * cfqd->cfq_slice_idle;



		cfq_mark_cfqq_idle_window(cfqq);

		cfq_mark_cfqq_prio_changed(cfqq);

		cfq_mark_cfqq_queue_new(cfqq);
@@ -1585,11 +1585,6 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 
		return 1;

	if (!cfq_cfqq_wait_request(new_cfqq))

		return 0;

	/*

	 * if it doesn't have slice left, forget it

	 */

	if (new_cfqq->slice_left < cfqd->cfq_slice_idle)

		return 0;

	/*

	 * if the new request is sync, but the currently running queue is

	 * not, let the sync request have priority.
@@ -1614,9 +1609,6 @@ static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 
{

	cfq_slice_expired(cfqd, 1);



	if (!cfqq->slice_left)

		cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;



	/*

	 * Put the new queue at the front of the of the current list,

	 * so we know that it will be selected next.