Commit 30e0dc28 authored Oct 20, 2008 by Jens Axboe

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>

parent 31dcfab0

block/cfq-iosched.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -1136,12 +1136,8 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
		if (cfq_class_idle(cfqq))
		max_dispatch = 1;

		if (cfqq->dispatched >= max_dispatch) {
		if (cfqd->busy_queues > 1)
		if (cfqq->dispatched >= max_dispatch && cfqd->busy_queues > 1)
		break;
		if (cfqq->dispatched >= 4 * max_dispatch)
		break;
		}

		if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
		break;

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