Commit 05e90283 authored Dec 20, 2017 by Paolo Valente Committed by Jens Axboe Jan 05, 2018

block, bfq: add missing rq_pos_tree update on rq removal



If two processes do I/O close to each other, then BFQ merges the
bfq_queues associated with these processes, to get a more sequential
I/O, and thus a higher throughput.  In this respect, to detect whether
two processes are doing I/O close to each other, BFQ keeps a list of
the head-of-line I/O requests of all active bfq_queues.  The list is
ordered by initial sectors, and implemented through a red-black tree
(rq_pos_tree).

Unfortunately, the update of the rq_pos_tree was incomplete, because
the tree was not updated on the removal of the head-of-line I/O
request of a bfq_queue, in case the queue did not remain empty. This
commit adds the missing update.

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent f0ba5ea2

block/bfq-iosched.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1627,6 +1627,8 @@ static void bfq_remove_request(struct request_queue *q,
		rb_erase(&bfqq->pos_node, bfqq->pos_root);
		bfqq->pos_root = NULL;
		}
		} else {
		bfq_pos_tree_add_move(bfqd, bfqq);
		}

		if (rq->cmd_flags & REQ_META)