Arch Linux

aexl

Member

From: Basel, Switzerland

Registered: 2014-03-19

Posts: 28

Use cfq in the regular Linux kernel and bfq in linux-ck

I have the regular Linux kernel and linux-ck installed. Now I would like to use the cfq-IO-scheduler in linux and bfq in linux-ck. How can I achieve this without setting "elevator=..." in grub. Is there a way to do this in udev? At the moment I have a udev rule, which activates cfq. Is there a way, to load cfq, if I boot linux, and bfq, if I boot linux-ck?

karol

Archivist

Registered: 2009-05-06

Posts: 25,440

Re: Use cfq in the regular Linux kernel and bfq in linux-ck

I'm not sure I understand, I'm not using grub.
In syslinux I can have many menu items, pointing to various configurations of kernel images and kernel commandline options. What's wrong with doing it like this?

If you're using /etc/tmpfiles.d/set_IO_scheduler.conf https://wiki.archlinux.org/index.php/Li … ed_devices and you've set it to bfq, then you'll get a warning at boot when you pick the stock linux w/o bfq and the I/O scheduler will be set to the default cfq then.

WonderWoofy

Member

From: Los Gatos, CA

Registered: 2012-05-19

Posts: 8,414

Re: Use cfq in the regular Linux kernel and bfq in linux-ck

If you're using /etc/tmpfiles.d/set_IO_scheduler.conf https://wiki.archlinux.org/index.php/Li … ed_devices and you've set it to bfq, then you'll get a warning at boot when you pick the stock linux w/o bfq and the I/O scheduler will be set to the default cfq then.

I would imagine that if you decided to use a udev rule to set this instead, you would also simply get an error with the Arch kernel and end up back on cfq.  But I think the most elegant way to do it would be to simply use the kernel command line for a linux-ck specific entry.

clfarron4

Member

From: London, UK

Registered: 2013-06-28

Posts: 2,175

Website

Re: Use cfq in the regular Linux kernel and bfq in linux-ck

If you're using /etc/tmpfiles.d/set_IO_scheduler.conf https://wiki.archlinux.org/index.php/Li … ed_devices and you've set it to bfq, then you'll get a warning at boot when you pick the stock linux w/o bfq and the I/O scheduler will be set to the default cfq then.

I would imagine that if you decided to use a udev rule to set this instead, you would also simply get an error with the Arch kernel and end up back on cfq.  But I think the most elegant way to do it would be to simply use the kernel command line for a linux-ck specific entry.

Last time I booted the ARCH kernel with the BFQ disk scheduler, it kicked out an error saying that BFQ wasn't a valid  disk scheduler and that it was falling back to CFQ.

I still think that the nicer solution is to pass it as a bootloader parameter because you can select which kernels boot with what.

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