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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: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Shaohua Li 2010-11-08 15:01:03 +01:00 committed by Jens Axboe
parent c1e44756fd
commit d2d59e18a1
1 changed files with 22 additions and 1 deletions
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23
block/cfq-iosched.c
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@ -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))
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))
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);
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);
}
}
/*