I/O scheduling for single-queue devices

Posted Oct 13, 2018 17:46 UTC (Sat) by josh (subscriber, #17465)
Parent article: I/O scheduling for single-queue devices

For a device that does have multiple queues, does the kernel use "none" or "mq-deadline" by default? I have a recent NVMe drive, and the kernel seems to default to "none"; I'm wondering if that's the right default.

I/O scheduling for single-queue devices

Posted Oct 15, 2018 9:26 UTC (Mon) by jan.kara (subscriber, #59161) [Link] (3 responses)

What does your /sys/block/<dev>/queue/scheduler show?

I/O scheduling for single-queue devices

Posted Oct 15, 2018 12:30 UTC (Mon) by timokokk (subscriber, #52029) [Link] (1 responses)

For me it shows as:

$ cat /sys/block/nvme0n1/queue/scheduler
[none] mq-deadline kyber bfq

Running still 4.18.1

I/O scheduling for single-queue devices

Posted Oct 16, 2018 12:27 UTC (Tue) by timokokk (subscriber, #52029) [Link]

Seems that there is only one list for IO schedulers, both normal and multi-queue schedulers are put on the same list. You can only choose default for the normal schedulers, not for the MQ ones. So apparently the default for mq-scheduler is thus nop as there is no way to set it up at compile time.

I/O scheduling for single-queue devices

Posted Oct 15, 2018 15:11 UTC (Mon) by josh (subscriber, #17465) [Link]

$ cat /sys/block/nvme0n1/queue/scheduler
[none] mq-deadline