Messages in this thread Patch in this message | | | Date | Mon, 26 Oct 2009 17:16:24 +0800 | From | Shaohua Li <> | Subject | [RFC]cfq-iosched: improve hw_tag detection |
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If active queue hasn't enough requests and idle window opens, cfq will not dispatch sufficient requests to hardware. In such situation, current code will zero hw_tag. But this is because cfq doesn't dispatch enough requests instead of hardware queue doesn't work. Don't zero hw_tag in such case.
Signed-off-by: Shaohua Li <shaohua.li@intel.com> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 069a610..0467049 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -2166,6 +2166,8 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq) */ static void cfq_update_hw_tag(struct cfq_data *cfqd) { + struct cfq_queue *cfqq = cfqd->active_queue; + if (rq_in_driver(cfqd) > cfqd->rq_in_driver_peak) cfqd->rq_in_driver_peak = rq_in_driver(cfqd); @@ -2173,6 +2175,16 @@ static void cfq_update_hw_tag(struct cfq_data *cfqd) rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN) return; + /* + * If active queue hasn't enough requests and can idle, cfq might not + * dispatch sufficient requests to hardware. Don't zero hw_tag in this + * case + */ + if (cfqq && cfq_cfqq_idle_window(cfqq) && + cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] < + CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN) + return; + if (cfqd->hw_tag_samples++ < 50) return;
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