On 2022/11/21 23:56, Ming Lei wrote: > Either ublk_can_use_task_work() is true or not, io commands are > forwarded to ublk server in reverse order, since llist_add() is > always to add one element to the head of the list. > > Even though block layer doesn't guarantee request dispatch order, > requests should be sent to hardware in the sequence order generated > from io scheduler, which usually considers the request's LBA, and > order is often important for HDD. > > So forward io commands in the sequence made from io scheduler by > aligning task work with current io_uring command's batch handling, > and it has been observed that both can get similar performance data > if IORING_SETUP_COOP_TASKRUN is set from ublk server. > > Reported-by: Andreas Hindborg <andreas.hindborg@xxxxxxx> > Cc: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> I have tested this with dd. Looks like we get the correct order: ublk_queue_rq: qid 0 tag 2 sect 12288 __ublk_rq_task_work: complete: op 33, qid 0 tag 2 io_flags 1 addr 7ff16699e000 sect 12288 ublk_queue_rq: qid 0 tag 5 sect 13312 __ublk_rq_task_work: complete: op 33, qid 0 tag 5 io_flags 1 addr 7ff166818000 sect 13312 ublk_queue_rq: qid 0 tag 4 sect 14336 __ublk_rq_task_work: complete: op 33, qid 0 tag 4 io_flags 1 addr 7ff16689a000 sect 14336 ublk_queue_rq: qid 0 tag 6 sect 15360 __ublk_rq_task_work: complete: op 33, qid 0 tag 6 io_flags 1 addr 7ff166796000 sect 15360 Reviewed-by: ZiyangZhang <ZiyangZhang@xxxxxxxxxxxxxxxxx> Regards, Zhang
