Re: Default I/O scheduler for 2.6.12 AMD64?

[Giacomo Mulas <gmulas@ca.astro.it>]

On Wed, 16 Nov 2005, Joost Kraaijeveld wrote:

> How can I see what the default I/O scheduler is for 2.6.12 AMD64 and how
> do I change the default scheduler?

Browse the /sys/block/<your device name>/queue directory, you will find a
file named "scheduler", which you can read to see the active scheduler on
that device and write to change it. It can be changed on the fly at runtime.
The parameters of the running scheduler can be seen and changed by
reading/writing the files in the directory /sys/block/<your device
name>/queue/iosched directory. A good idea, if you want to really be picky
and optimise things for every single device individually, may be to install
the sysfsutils package and edit its /etc/sysfs.conf configuration file, where 
you can set values, to be loaded duting the boot sequence, for any tunable
parameter in the /sys pseudo file system.

If you want to change the default scheduler at boot (this was probably your
question), you can use a kernel parameter at boot time, namely
"elevator=<your chosen default scheduler>", i.e. elevator=cfq.

Bye
Giacomo

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Giacomo Mulas <gmulas@ca.astro.it>
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