elevator= parameter suddenly appeared at boot

statguy · 11-08-2007, 10:50 AM

I'm using OpenSUSE 10.2. I recently updated the kernel to 2.6.18.8-0.7. This was a security update.

Now I have noticed that when the grub boot menu displays that there is "elevator=" on the command line parameters. It was probably there since the update, I just never noticed.

From

/usr/src/linux/Documentation/kernel-parameters.txt

I find

Code:

elevator=       [IOSCHED]
                Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
                See Documentation/block/as-iosched.txt and
                Documentation/block/deadline-iosched.txt for details.

So, it has something to do with the IO scheduler.

Why did this suddenly appear? Should I remove it?
Since this last kernel upgrade I have had a number
of total freezes while running on battery and I
now wonder if it might be related to this parameter.
Since I had not noticed it until today, I had just
been booting without setting the parameter.

marozsas · 11-08-2007, 12:08 PM

Quote:

Originally Posted by statguy

So, it has something to do with the IO scheduler.

You are right.

Quote:

Originally Posted by statguy

Why did this suddenly appear?

This is a new feature you got with the kernel upgrade.

Quote:

Originally Posted by statguy

Should I remove it?

left it as is. The default applies.

Quote:

Originally Posted by statguy

Since this last kernel upgrade I have had a number
of total freezes while running on battery and I
now wonder if it might be related to this parameter.

I don't known. You can test one of the options and see if you get better stability. My system is a big server and I realize by experimentation that elevator=anticipatory gives me more performance in reading. So I change the /boot/grub/menu.lst and add "anticipatory" as default value.

statguy · 11-08-2007, 07:33 PM

Quote:

Originally Posted by marozsas

I don't known. You can test one of the options and see if you get better stability. My system is a big server and I realize by experimentation that elevator=anticipatory gives me more performance in reading. So I change the /boot/grub/menu.lst and add "anticipatory" as default value.

Thank you for the concise, helpful reply. I will try different values. FWIW, the default was cfq. I also have noop and deadline as options. The description in

Code:

/usr/src/linux/Documentation/block/as-iosched.txt

is beyond me, so do you have any explanations/thoughts on the various options?

syg00 · 11-08-2007, 08:15 PM

Try this for some background.

statguy · 11-20-2007, 07:54 PM

I have tried all of the different elevator= choices and none of them solved my freezing problem on battery power.

So, I guess this is not the source of the problem.