[LAU] Ubuntu: changing realtime priority of irqs

[Thomas Kuther]

On Sa, 21.07.07 14:03 Atte André Jensen <atte.jensen at gmail.com> 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":

I only get processes for IRQ's on -rt patched kernels
Maybe ubuntustudio uses a standard patched-to-death ubuntu kernel with
hz 1000 and LLD preempt?


> 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?
> 
> -- 
> peace, love & harmony
> Atte
> 
> http://atte.dk       | http://myspace.com/attejensen 
> http://anagrammer.dk | http://atte.dk/compositions
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