On 12/02/2016 08:15 PM, Jens Axboe wrote: > 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 BTW, didn't include the patch for SCSI. You need the below to enable scheduling on SCSI devices. diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index aedcec3..47a5c87 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -2121,7 +2121,7 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) shost->tag_set.queue_depth = shost->can_queue; shost->tag_set.cmd_size = cmd_size; shost->tag_set.numa_node = NUMA_NO_NODE; - shost->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE | BLK_MQ_F_SQ_SCHED; + shost->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE; shost->tag_set.flags |= BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy); shost->tag_set.driver_data = shost; -- 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
