I hacked up some support for registering blk-mq capable IO schedulers, and when that was done, I adapted deadline to work with it as a new mq-deadline scheduler. Basically this is similar to the legacy scheduling patches I posted recently, in that we setup a list of fake requests (I called them shadows) that the IO scheduler works on. We then transform those into a real blk-mq request, when we have to dispatch to hardware. There's a hack in place to make this work with the flush/fua requests, as those bypass the regular software queue insertion. For now we simply ensure that we allocate a real request for those. Howeer, I'd prefer if we simply inserted the request as we usually would, and then start the flush state machinery when we pull the request out of the queue. That would both be cleaner from a flush perspective, and from the scheduling side as well. I'm reusing the existing elevator interface, just augmenting that with mq_ops and a ->uses_mq so we can tell which is which. They show up automatically, for instance on a scsi-mq device: $ cat /sys/block/sda/queue/scheduler [mq-deadline] none vs just a legacy device: $ cat /sys/block/nullb0/queue/scheduler noop deadline [cfq] Changing schedulers is done in the same way as it always has, by echoing into the 'scheduler' file. For MQ, there's a 'none' setting as well that isn't a real scheduler, it simply turns off the scheduler. Handy for comparison. Obviously a direct deadline adaptation has performance implications, so it can be improved. A _real_ MQ scheduler is forth coming, which will sit on top of this interface. Paolo, for BFQ, this is the interface you should target. Let me know if you have any questions about how it works. block/Kconfig.iosched | 6 block/Makefile | 3 block/blk-core.c | 3 block/blk-exec.c | 3 block/blk-flush.c | 7 block/blk-mq-sched.c | 243 ++++++++++++++++++ block/blk-mq-sched.h | 168 ++++++++++++ block/blk-mq-tag.c | 1 block/blk-mq.c | 241 ++++++++++-------- block/blk-mq.h | 33 -- block/elevator.c | 140 +++++++--- block/mq-deadline.c | 622 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/blk-mq.h | 3 include/linux/elevator.h | 30 ++ 14 files changed, 1331 insertions(+), 172 deletions(-) -- 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
