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Commit d2d59e18 authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
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cfq-iosched: schedule dispatch for noidle queue 



A queue is idle at cfq_dispatch_requests(), but it gets noidle later. Unless
other task explictly does unplug or all requests are drained, we will not
deliever requests to the disk even cfq_arm_slice_timer doesn't make the
queue idle. For example, cfq_should_idle() returns true because of
service_tree->count == 1, and then other queues are added. Note, I didn't
see obvious performance impacts so far with the patch, but just thought
this could be a problem.

Signed-off-by: default avatarShaohua Li <shaohua.li@intel.com>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent c1e44756

block/cfq-iosched.c

+22 −1
Original line number Original line Diff line number Diff line
@@ -3255,6 +3255,10 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, 
	if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))

	if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))

		return true;

		return true;





	/* An idle queue should not be idle now for some reason */

	if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))

		return true;



	if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))

	if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))

		return false;

		return false;
@@ -3508,8 +3512,25 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq) 
		}

		}

	}

	}





	if (!cfqd->rq_in_driver)

	if (!cfqd->rq_in_driver) {

		cfq_schedule_dispatch(cfqd);

		cfq_schedule_dispatch(cfqd);

		return;

	}

	/*

	 * A queue is idle at cfq_dispatch_requests(), but it gets noidle

	 * later. We schedule a dispatch if the queue has no requests,

	 * otherwise the disk is actually in idle till all requests

	 * are finished even cfq_arm_slice_timer doesn't make the queue idle

	 * */

	cfqq = cfqd->active_queue;

	if (!cfqq)

		return;



	if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq) &&

	    (!cfqd->cfq_group_idle || cfqq->cfqg->nr_cfqq > 1)) {

		cfq_del_timer(cfqd, cfqq);

		cfq_schedule_dispatch(cfqd);

	}

}

}





/*

/*