[LAU] Ubuntu: changing realtime priority of irqs

[David Causse]

Atte André Jensen a écrit :
> Hi
>
> I trying out ubuntu with ubuntustudio kernel. In debian I always set the
> priority of the IRQ's using
>
> chrt -f -p 85 `pidof "IRQ 8"`
>
> However that doesn't work in ubuntu. The reason is that there seems to
> be no process named "IRQ 8":
>
> atte at ajstrup:~$ ps aux | grep -i IRQ
> root         3  0.0  0.0      0     0 ?        SN   13:43   0:00
> [ksoftirqd/0]
> atte      6274  0.0  0.0   2884   772 pts/0    R+   13:51   0:00 grep -i
> irq
>   
Hi,

Your ubuntu kernel doesn't support this feature, to be sure try to look 
at /proc/config.gz
zcat /proc/config.gz | grep PREEMPT

You must have something like this :
CONFIG_PREEMPT_HARDIRQS=y

It appears that the default kernel used by Ubuntu studio 
(linux-image-lowlatency) is not patched against the Ingo's RT patch 
(required to do what you want)
http://www.mail-archive.com/debian-multimedia@lists.debian.org/msg01756.html
The RT kernel package seems to be linux-image-2.6.21-1-multimedia-486 
<http://apt.64studio.com/64studio/testing/pool/main/l/linux-2.6/linux-image-2.6.21-1-multimedia-486_2.6.21-2_i386.deb>

David C.