• Ming Lei's avatar
    blk-mq-sched: fix performance regression of mq-deadline · 32825c45
    Ming Lei authored
    When mq-deadline is taken, IOPS of sequential read and
    seqential write is observed more than 20% drop on sata(scsi-mq)
    devices, compared with using 'none' scheduler.
    
    The reason is that the default nr_requests for scheduler is
    too big for small queuedepth devices, and latency is increased
    much.
    
    Since the principle of taking 256 requests for mq scheduler
    is based on 128 queue depth, this patch changes into
    double size of min(hw queue_depth, 128).
    Signed-off-by: 's avatarMing Lei <ming.lei@redhat.com>
    Signed-off-by: 's avatarJens Axboe <axboe@kernel.dk>
    32825c45