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Ming Lei authored
Before blk-mq is introduced, I/O is merged to elevator before being putted into plug queue, but blk-mq changed the order and makes merging to sw queue basically impossible. Then it is observed that throughput of sequential I/O is degraded about 10%~20% on virtio-blk in the test[1] if mq-deadline isn't used. This patch moves the bio merging per sw queue before plugging, like what blk_queue_bio() does, and the performance regression is fixed under this situation. [1]. test script: sudo fio --direct=1 --size=128G --bsrange=4k-4k --runtime=40 --numjobs=16 --ioengine=libaio --iodepth=64 --group_reporting=1 --filename=/dev/vdb --name=virtio_blk-test-$RW --rw=$RW --output-format=json RW=read or write Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
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