Linux's Multi-Queue Block Code Still Presenting Some Performance Regressions

[Vistaus]

I don't remember, but here's what I've done:

Linux command line addon: scsi_mod.use_blk_mq=1
(you can use dm_mod as well for the device mapper I believe, I don't use it)
udev rule: ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{queue/scheduler}="bfq"
retrigger udev: udevadm control --reload && udevadm trigger
or simply restart the system.

Adjust as needed for kyber/your system.

The simplest way to change your scheduler is of course: echo kyber >| /sys/block/sdX/queue/scheduler (replace X appropriately).
That will only work once you are on blk_mq, but that seems to be your case already so that's fine.

Although, one think to check, just in case, make sure you have kyber available, if it's not in: cat /sys/block/sd*/queue/scheduler, you may have to rebuild your kernel.

Thank you so much! One question though: in what file do I put that udev rule? 'Cause there seem to be a lot of them in /usr/lib64/udev/rules.d

[geearf]

Thank you so much! One question though: in what file do I put that udev rule? 'Cause there seem to be a lot of them in /usr/lib64/udev/rules.d

You're welcome, but don't put anything in /usr, that's not for you
I put it in /etc/udev/rules.d/60-schedulers.rules


Did it work?

[Vistaus]

You're welcome, but don't put anything in /usr, that's not for you
I put it in /etc/udev/rules.d/60-schedulers.rules


Did it work?

Yes, that worked! Thank you so much for all of your help!

[geearf]

Yes, that worked! Thank you so much for all of your help!

You're very welcome!

On my end I decided to move back away from blk_mq till Ming's fixes make it (or till I move to 4.13 and use the patches available..., they didn't apply to 4.12...).