[LAU] Ubuntu: changing realtime priority of irqs

[Florian Schmidt]

On Saturday 21 July 2007, Atte André Jensen wrote:
> 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
>
> Whereas on debian I would get:
>
> atte at ajstrup:~$ ps aux | grep IRQ
> root        18  0.2  0.0      0     0 ?        S<   13:34   0:00 [IRQ 9]
> root       261  0.0  0.0      0     0 ?        S<   13:34   0:00 [IRQ 4]
> root       286  0.0  0.0      0     0 ?        S<   13:34   0:00 [IRQ
> 12]
> root       300  0.0  0.0      0     0 ?        S<   13:34   0:00 [IRQ 1]
> root       608  0.0  0.0      0     0 ?        S<   13:34   0:00 [IRQ
> 11]
> root       761  0.0  0.0      0     0 ?        S<   13:34   0:00 [IRQ
> 14]
> root       787  0.0  0.0      0     0 ?        S<   13:34   0:00 [IRQ
> 15]
> root      1592  0.0  0.0      0     0 ?        S<   13:34   0:00 [IRQ 8]
> root      1593  0.0  0.0      0     0 ?        S<   13:34   0:00 [IRQ 7]
> root      1683  0.0  0.0      0     0 ?        S<   13:34   0:00 [IRQ
> 10]
> atte      4672  0.0  0.0   2848   704 pts/1    R+   13:41   0:00 grep
> IRQ
>
> I suspect it has something to do with "ksoftirqd" which according to the
> man page seems to be a daemon handling irqs.
>
> http://tapas.affenbande.org/wordpress/?page_id=40 also doesn't seem to
> take ksoftirqd into account.
>
> So my question is: How do I set the priorities in ubuntu? Is it
> possible/clever/stupid to get rid og ksoftirqd and get things working
> the way I'm used to under debian, and if so how?


No, ksoftirq shouldn't have anything to do with it.. HEre's what the output of 
that is on my system:

~$ ps aux|grep IRQ
root        41  0.0  0.0      0     0 ?        S<   Jul21   0:00 [IRQ-9]
root       775  0.0  0.0      0     0 ?        S<   Jul21   0:00 [IRQ-8]
root       812  0.0  0.0      0     0 ?        S<   Jul21   0:09 [IRQ-12]
root       813  0.0  0.0      0     0 ?        S<   Jul21   0:00 [IRQ-1]
root      2032  0.0  0.0      0     0 ?        S<   Jul21   0:00 [IRQ-16]
root      2110  0.0  0.0      0     0 ?        S<   Jul21   0:00 [IRQ-17]
root      2152  0.0  0.0      0     0 ?        S<   Jul21   0:03 [IRQ-14]
root      2192  0.0  0.0      0     0 ?        S<   Jul21   0:02 [IRQ-15]
root      2745  0.4  0.0      0     0 ?        S<   Jul21   3:42 [IRQ-18]
root      3629  0.0  0.0      0     0 ?        S<   Jul21   0:00 [IRQ-7]
root      3785  0.1  0.0      0     0 ?        S<   Jul21   0:55 [IRQ-19]
tapas    14252  0.0  0.0   2884   752 pts/1    R+   01:35   0:00 grep IRQ

~$ uname -a
Linux balabala 2.6.20-16-realtime #2 SMP PREEMPT Fri Jun 15 04:43:25 CEST 2007 
i686 GNU/Linux


Let's see your uname -a output please..

Flo



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