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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>
This commit is contained in:
Paolo Valente 2017-12-20 12:38:31 +01:00 committed by Jens Axboe
parent f0ba5ea2fe
commit 05e9028356
1 changed files with 2 additions and 0 deletions
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2
block/bfq-iosched.c
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@ -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)