cfq-iosched: remove limit of dispatch depth of max 4 times quantum
This basically limits the hardware queue depth to 4*quantum at any point in time, which is 16 with the default settings. As CFQ uses other means to shrink the hardware queue when necessary in the first place, there's really no need for this extra heuristic. Additionally, it ends up hurting performance in some cases. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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@ -1136,12 +1136,8 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
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if (cfq_class_idle(cfqq))
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if (cfq_class_idle(cfqq))
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max_dispatch = 1;
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max_dispatch = 1;
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if (cfqq->dispatched >= max_dispatch) {
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if (cfqq->dispatched >= max_dispatch && cfqd->busy_queues > 1)
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if (cfqd->busy_queues > 1)
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break;
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break;
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if (cfqq->dispatched >= 4 * max_dispatch)
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break;
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}
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if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
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if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
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break;
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break;
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