virtio_blk: reverse request order in virtio_queue_rqs

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[ Upstream commit 7f212e997e ]

blk_mq_flush_plug_list submits requests in the reverse order that they
were submitted, which leads to a rather suboptimal I/O pattern
especially in rotational devices. Fix this by rewriting virtio_queue_rqs
so that it always pops the requests from the passed in request list, and
then adds them to the head of a local submit list. This actually
simplifies the code a bit as it removes the complicated list splicing,
at the cost of extra updates of the rq_next pointer. As that should be
cache hot anyway it should be an easy price to pay.

Fixes: 0e9911fa76 ("virtio-blk: support mq_ops->queue_rqs()")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241113152050.157179-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Christoph Hellwig 2024-11-13 16:20:42 +01:00 • committed by Greg Kroah-Hartman

parent 5198992912

commit b2c36fa9ac

1 changed files with 21 additions and 25 deletions

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drivers/block/virtio_blk.c

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