Commit 25776e35 authored by Jens Axboe's avatar Jens Axboe
Browse files

[PATCH] cfq-iosched: Detect hardware queueing 



If the hardware is doing real queueing, decide that it's worthless to
idle the hardware. It does reasonable simultaneous io in that case
anyways, and the idling hurts some work loads.

Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent 12e9fddd

block/cfq-iosched.c

+13 −2
Original line number Diff line number Diff line
@@ -133,6 +133,7 @@ struct cfq_data { 
	mempool_t *crq_pool;



	int rq_in_driver;

	int hw_tag;



	/*

	 * schedule slice state info
@@ -664,6 +665,15 @@ static void cfq_activate_request(request_queue_t *q, struct request *rq) 
	struct cfq_data *cfqd = q->elevator->elevator_data;



	cfqd->rq_in_driver++;



	/*

	 * If the depth is larger 1, it really could be queueing. But lets

	 * make the mark a little higher - idling could still be good for

	 * low queueing, and a low queueing number could also just indicate

	 * a SCSI mid layer like behaviour where limit+1 is often seen.

	 */

	if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)

		cfqd->hw_tag = 1;

}



static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
@@ -1465,6 +1475,7 @@ retry: 
		 * 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);
@@ -1656,7 +1667,7 @@ 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)

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

		enable_idle = 0;

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

		if (cic->ttime_mean > cfqd->cfq_slice_idle)

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