cfq-iosched: Fix the incorrect timeslice accounting with forced_dispatch
When CFQ dispatches requests forcefully due to a barrier or changing iosched, it runs through all cfqq's dispatching requests and then expires each queue. However, it does not activate a cfqq before flushing its IOs resulting in using stale values for computing slice_used. This patch fixes it by calling activate queue before flushing reuqests from each queue. This is useful mostly for barrier requests because when the iosched is changing it really doesnt matter if we have incorrect accounting since we're going to break down all structures anyway. We also now expire the current timeslice before moving on with the dispatch to accurately account slice used for that cfqq. Signed-off-by: Divyesh Shah<dpshah@google.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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@ -2205,10 +2205,13 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd)
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struct cfq_queue *cfqq;
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int dispatched = 0;
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while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL)
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dispatched += __cfq_forced_dispatch_cfqq(cfqq);
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/* Expire the timeslice of the current active queue first */
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cfq_slice_expired(cfqd, 0);
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while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
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__cfq_set_active_queue(cfqd, cfqq);
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dispatched += __cfq_forced_dispatch_cfqq(cfqq);
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}
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BUG_ON(cfqd->busy_queues);
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cfq_log(cfqd, "forced_dispatch=%d", dispatched);
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