nvme-pci: reverse request order in nvme_queue_rqs

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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 nvme_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: d62cbcf62f ("nvme: add support for mq_ops->queue_rqs()")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241113152050.157179-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Christoph Hellwig 2024-11-13 16:20:41 +01:00 • committed by Jens Axboe

parent e559ee0226

commit beadf00885

1 changed files with 17 additions and 22 deletions

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drivers/nvme/host/pci.c

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