This is by no means done, but it seems to work well enough that I thought I'd send it out for others to take a look at and play with. Basically this allows blk-mq managed devices to run the legacy IO schedulers, unmodified. The only requirement is that the blk-mq device has to be single queue for now, though that limitation would be rather simple to lift. Since this is a debug patch, the default scheduler is deadline. You can switch that to the other configured schedulers, as you would with non-mq devices. Here's an example of a scsi-mq device that is running deadline, and being switched to CFQ online: root@leopard:~# cat /sys/block/sda/mq/0/tags nr_tags=31, reserved_tags=0, bits_per_word=4 nr_free=31, nr_reserved=0 active_queues=0 root@leopard:~# cat /sys/block/sda/queue/scheduler noop [deadline] cfq root@leopard:~# echo cfq > /sys/block/sda/queue/scheduler root@leopard:~# cat /sys/block/sda/queue/scheduler noop deadline [cfq] Testing welcome. There's certainly room for improvement here, so I'm mostly interested in grave performance issues or crashes, if any. Can also be viewed/fetched via git: git://git.kernel.dk/linux-block for-4.11/blk-mq-legacy-sched -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
