Kyber io scheduler for nvme

General system Kernel, boot, graphics & hardware
1

cachyos has announced that they will start using kyber as the default io scheduler for nvme.

That made me dig into this topic a little deeper. I always used io scheduler “none” for nvme or ssd. But it looks like that kyber has some benefits for fast nvme. I found this interesting article:

In the conclusion they say:

"In this paper, we investigate if the Linux I/O schedulers fit modern
NVMe SSDs. Our results show that BFQ and MQ-Deadline have
significantly high CPU overhead and scalability issues caused by
locking. Thus, we suggest that BFQ and MQ-Deadline should not
be used with these SSDs. Kyber has lower CPU overhead than BFQ
and MQ-Deadline with near-linear scalability and thus is the best fit
of these SSDs. However, the parameters of Kyber need to be tuned
carefully or Kyber harms the performance."

I am not yet clear which kyber parameters they are talking about, but I have decided to give it a try.

I am just throwing this out here for anybody who is interested.

2

I can’t imagine I will notice the difference, but I swapped over to kyber, and so far haven’t noticed the difference :rofl:

3

As is tradition. Cachy changing the I/O scheduler once in a while. Two years ago it was already Kyber, then they changed it to None, now it’s Kyber again.

It’s a little bit of a joke right now. Cachy does good things, don’t get me wrong, but honestly, on some aspects of their performance seeking journey they miss the goal and act … silly.

4

I am not so sure if they are missing the goal here. From what I have read so far kyber is a very good - probably the best - low latency io scheduler for nvme devices.

The liquorix kernel is doing the same by the way:

"Optimized Disk I/O: Uses Kyber for multiqueue devices and BFQ for single queue devices, providing best responsiveness under high IO."

And pop!_os is doing the same:

5

any advice about how to configure this scheduler, the linked paper talks about tuning? or I should copy the one from cachyos?

6

You could just copy the Cachy rules if the same behavior is desired. That’s just how you dial in those changes, see also e.g. https://wiki.archlinux.org/title/Improving_performance#Changing_I/O_scheduler