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heisenberg

Member

Registered: 2017-05-27

Posts: 87

[SOLVED] Doubt about BFQ scheduler on 4.12 kernel

Hi, on my laptop I'm running the stable kernel (4.12.4-1-ARCH). I read somewhere that I could enable BFQ on that version.

But apparently it's not avaible:

[heisenberg@arch-asus ~]$ cat /sys/block/sda/queue/scheduler
noop deadline [cfq] 

So... what am I doing wrong ? How can I enable BFQ (on boot, not "on-the-fly") ?

Last edited by heisenberg (2017-08-11 03:00:12)

jasonwryan

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From: .nz

Registered: 2009-05-09

Posts: 30,424

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Re: [SOLVED] Doubt about BFQ scheduler on 4.12 kernel

https://unix.stackexchange.com/question … -scheduler

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heisenberg

Member

Registered: 2017-05-27

Posts: 87

Re: [SOLVED] Doubt about BFQ scheduler on 4.12 kernel

Thanks! I got confused from https://wiki.archlinux.org/index.php/Im … schedulers, I was thinking it was a completely different scheduler.

What changes if I add also "dm_mod.use_blk_mq=y" ??

loqs

Member

Registered: 2014-03-06

Posts: 17,368

Re: [SOLVED] Doubt about BFQ scheduler on 4.12 kernel

What changes if I add also "dm_mod.use_blk_mq=y" ??

Nothing unless you use the dm_multipath target no other dm targets support mq.
As a note should it not be dm_mod.use_blk_mq=0
Also do not try and globally set the io scheduler to bfq with elevator=bfq,
if scsci_mod.use_blk_mq is set to 1 it will not do anything if it is set to 0 the system will not boot.

heisenberg

Member

Registered: 2017-05-27

Posts: 87

Re: [SOLVED] Doubt about BFQ scheduler on 4.12 kernel

Thanks, that's the situation now (added just "scsi_mod.use_blk_mq=1"):

[heisenberg@arch-asus ~]$ cat /sys/block/sda/queue/scheduler
[mq-deadline] kyber bfq none

How do I choose bfq automatically on boot ?

p.s. I'm using systemd-boot, not grub.

Last edited by heisenberg (2017-08-10 10:48:42)

loqs

Member

Registered: 2014-03-06

Posts: 17,368

Re: [SOLVED] Doubt about BFQ scheduler on 4.12 kernel

Use a udev rule the link jasonwryan documents creating one Improving_performance#Persisting_the_change also covers it.
To apply it to all devices you would want to remove 'ATTR{queue/rotational}=="0", ' from the arch wiki example.

heisenberg

Member

Registered: 2017-05-27

Posts: 87

Re: [SOLVED] Doubt about BFQ scheduler on 4.12 kernel

Perfect. I'll try it and mark the thread as solved^^

Though, making that udev rule, may create any boot issue if/when I'll boot the lts kernel ? (because BFQ should not be avaible here I guess).

EDIT: Tried myself, lts boots and uses deadline as i/o scheduler.

Last edited by heisenberg (2017-08-11 02:59:51)