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Commit caaa5f9f authored by Jens Axboe's avatar Jens Axboe Committed by Jens Axboe
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[PATCH] cfq-iosched: many performance fixes 



This is a collection of patches that greatly improve CFQ performance
in some circumstances.

- Change the idling logic to only kick in after a request is done and we
  are deciding what to do. Before the idling included the request service
  time, so it was hard to adjust. Now it's true think/idle time.

- Take advantage of TCQ/NCQ/queueing for seeky sync workloads, but keep
  it in control for sync and sequential (or close to) workloads.

- Expire queues immediately and move on to other busy queues, if we are
  not going to idle after the current one finishes.

- Don't rearm idle timer if there are no busy queues. Just leave the
  system idle.

Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent 35e6077c

block/cfq-iosched.c

+76 −40
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ static const int cfq_back_penalty = 2; /* penalty of a backwards seek */ 
static const int cfq_slice_sync = HZ / 10;

static int cfq_slice_async = HZ / 25;

static const int cfq_slice_async_rq = 2;

static int cfq_slice_idle = HZ / 70;

static int cfq_slice_idle = HZ / 125;



#define CFQ_IDLE_GRACE		(HZ / 10)

#define CFQ_SLICE_SCALE		(5)
@@ -906,6 +906,8 @@ static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd) 
	return cfqq;

}



#define CIC_SEEKY(cic) ((cic)->seek_mean > (128 * 1024))



static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)



{
@@ -939,7 +941,7 @@ static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq) 
	 * fair distribution of slice time for a process doing back-to-back

	 * seeks. so allow a little bit of time for him to submit a new rq

	 */

	if (sample_valid(cic->seek_samples) && cic->seek_mean > 131072)

	if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))

		sl = 2;



	mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
@@ -1038,8 +1040,10 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd) 
	 */

	if (!RB_EMPTY(&cfqq->sort_list))

		goto keep_queue;

	else if (cfq_cfqq_class_sync(cfqq) &&

		 time_before(now, cfqq->slice_end)) {

	else if (cfq_cfqq_dispatched(cfqq)) {

		cfqq = NULL;

		goto keep_queue;

	} else if (cfq_cfqq_class_sync(cfqq)) {

		if (cfq_arm_slice_timer(cfqd, cfqq))

			return NULL;

	}
@@ -1088,8 +1092,7 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	} while (dispatched < max_dispatch);



	/*

	 * if slice end isn't set yet, set it. if at least one request was

	 * sync, use the sync time slice value

	 * if slice end isn't set yet, set it.

	 */

	if (!cfqq->slice_end)

		cfq_set_prio_slice(cfqd, cfqq);
@@ -1100,7 +1103,8 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
	 */

	if ((!cfq_cfqq_sync(cfqq) &&

	    cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||

	    cfq_class_idle(cfqq))

	    cfq_class_idle(cfqq) ||

	    !cfq_cfqq_idle_window(cfqq))

		cfq_slice_expired(cfqd, 0);



	return dispatched;
@@ -1109,10 +1113,11 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
static int

cfq_forced_dispatch_cfqqs(struct list_head *list)

{

	int dispatched = 0;

	struct cfq_queue *cfqq, *next;

	struct cfq_rq *crq;

	int dispatched;



	dispatched = 0;

	list_for_each_entry_safe(cfqq, next, list, cfq_list) {

		while ((crq = cfqq->next_crq)) {

			cfq_dispatch_insert(cfqq->cfqd->queue, crq);
@@ -1120,6 +1125,7 @@ cfq_forced_dispatch_cfqqs(struct list_head *list) 
		}

		BUG_ON(!list_empty(&cfqq->fifo));

	}



	return dispatched;

}
@@ -1146,7 +1152,8 @@ static int 
cfq_dispatch_requests(request_queue_t *q, int force)

{

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

	struct cfq_queue *cfqq;

	struct cfq_queue *cfqq, *prev_cfqq;

	int dispatched;



	if (!cfqd->busy_queues)

		return 0;
@@ -1154,10 +1161,17 @@ cfq_dispatch_requests(request_queue_t *q, int force) 
	if (unlikely(force))

		return cfq_forced_dispatch(cfqd);



	cfqq = cfq_select_queue(cfqd);

	if (cfqq) {

	dispatched = 0;

	prev_cfqq = NULL;

	while ((cfqq = cfq_select_queue(cfqd)) != NULL) {

		int max_dispatch;



		/*

		 * Don't repeat dispatch from the previous queue.

		 */

		if (prev_cfqq == cfqq)

			break;



		cfq_clear_cfqq_must_dispatch(cfqq);

		cfq_clear_cfqq_wait_request(cfqq);

		del_timer(&cfqd->idle_slice_timer);
@@ -1166,10 +1180,19 @@ cfq_dispatch_requests(request_queue_t *q, int force) 
		if (cfq_class_idle(cfqq))

			max_dispatch = 1;



		return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);

		dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);



		/*

		 * If the dispatch cfqq has idling enabled and is still

		 * the active queue, break out.

		 */

		if (cfq_cfqq_idle_window(cfqq) && cfqd->active_queue)

			break;



		prev_cfqq = cfqq;

	}



	return 0;

	return dispatched;

}



/*
@@ -1375,25 +1398,29 @@ static inline void changed_ioprio(struct cfq_io_context *cic) 
{

	struct cfq_data *cfqd = cic->key;

	struct cfq_queue *cfqq;

	if (cfqd) {



	if (unlikely(!cfqd))

		return;



	spin_lock(cfqd->queue->queue_lock);



	cfqq = cic->cfqq[ASYNC];

	if (cfqq) {

		struct cfq_queue *new_cfqq;

			new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC,

						cic->ioc->task, GFP_ATOMIC);

		new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC, cic->ioc->task,

					 GFP_ATOMIC);

		if (new_cfqq) {

			cic->cfqq[ASYNC] = new_cfqq;

			cfq_put_queue(cfqq);

		}

	}



	cfqq = cic->cfqq[SYNC];

	if (cfqq)

		cfq_mark_cfqq_prio_changed(cfqq);



	spin_unlock(cfqd->queue->queue_lock);

}

}



/*

 * callback from sys_ioprio_set, irqs are disabled
@@ -1461,7 +1488,6 @@ cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, 
		 * set ->slice_left to allow preemption for a new process

		 */

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

		if (!cfqd->hw_tag)

		cfq_mark_cfqq_idle_window(cfqq);

		cfq_mark_cfqq_prio_changed(cfqq);

		cfq_init_prio_data(cfqq);
@@ -1653,7 +1679,8 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
{

	int enable_idle = cfq_cfqq_idle_window(cfqq);



	if (!cic->ioc->task || !cfqd->cfq_slice_idle || cfqd->hw_tag)

	if (!cic->ioc->task || !cfqd->cfq_slice_idle ||

	    (cfqd->hw_tag && CIC_SEEKY(cic)))

		enable_idle = 0;

	else if (sample_valid(cic->ttime_samples)) {

		if (cic->ttime_mean > cfqd->cfq_slice_idle)
@@ -1683,7 +1710,7 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 
		return 0;



	if (!cfqq)

		return 1;

		return 0;



	if (cfq_class_idle(cfqq))

		return 1;
@@ -1715,7 +1742,7 @@ static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq) 
		cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;



	cfqq->slice_end = cfqq->slice_left + jiffies;

	__cfq_slice_expired(cfqd, cfqq, 1);

	cfq_slice_expired(cfqd, 1);

	__cfq_set_active_queue(cfqd, cfqq);

}
@@ -1834,11 +1861,23 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq) 
			cfqq->service_last = now;

			cfq_resort_rr_list(cfqq, 0);

		}

		cfq_schedule_dispatch(cfqd);

	}



	if (cfq_crq_is_sync(crq))

	if (sync)

		crq->io_context->last_end_request = now;



	/*

	 * If this is the active queue, check if it needs to be expired,

	 * or if we want to idle in case it has no pending requests.

	 */

	if (cfqd->active_queue == cfqq) {

		if (time_after(now, cfqq->slice_end))

			cfq_slice_expired(cfqd, 0);

		else if (sync && RB_EMPTY(&cfqq->sort_list)) {

			if (!cfq_arm_slice_timer(cfqd, cfqq))

				cfq_schedule_dispatch(cfqd);

		}

	}

}



static struct request *
@@ -2106,11 +2145,8 @@ static void cfq_idle_slice_timer(unsigned long data) 
		 * only expire and reinvoke request handler, if there are

		 * other queues with pending requests

		 */

		if (!cfqd->busy_queues) {

			cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end);

			add_timer(&cfqd->idle_slice_timer);

		if (!cfqd->busy_queues)

			goto out_cont;

		}



		/*

		 * not expired and it has a request pending, let it dispatch