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Commit b9c8946b authored by Jens Axboe's avatar Jens Axboe
Browse files

cfq-iosched: fix the slice residual sign 



We should subtract the slice residual from the rb tree key, since
a negative residual count indicates that the cfqq overran its slice
the last time. Hence we want to add the overrun time, to position
it a bit further away in the service tree.

Reported-by: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 0b182d61

block/cfq-iosched.c

+7 −1
Original line number Diff line number Diff line
@@ -507,8 +507,14 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq, 
		} else

			rb_key += jiffies;

	} else if (!add_front) {

		/*

		 * Get our rb key offset. Subtract any residual slice

		 * value carried from last service. A negative resid

		 * count indicates slice overrun, and this should position

		 * the next service time further away in the tree.

		 */

		rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;

		rb_key += cfqq->slice_resid;

		rb_key -= cfqq->slice_resid;

		cfqq->slice_resid = 0;

	} else {

		rb_key = -HZ;