A feature for -lowlatency kernel?

ailo ailo.at at gmail.com
Thu Apr 21 15:59:07 UTC 2011

On 04/21/2011 04:47 PM, Артём Попов wrote:
> 2011/4/11 Alessio Igor Bogani <abogani at ubuntu.com>:
>> Dear Ubuntu Studio Developers,
>> 2011/3/25 Alessio Igor Bogani <abogani at ubuntu.com>:
>> [...]
>>>> So I could provide a -lowlatency kernel based on 39 kernel if enough
>>>> testers will offer theirs help. Sincerely I would want avoid to waste
>>>> time for make something that no one will use.
>> [...]
>> You can find the 39-lowlatency(*) kernel at
>> https://launchpad.net/~abogani/+archive/snmp++/+packages
>> I suggest to install it manually (so without add the PPA).
>> Now it's your turn testers! :-)
> I don't know how to run the proper tests/benchmarks, but I still get
> xruns with my firewire card. I've got the firewire_ohci irq shared
> between wifi, mmc and usb ports, so I added firewire_ohci to the rtirq
> configuration file.
> Qjackctl shows very high CPU load (~60%) when no clients are
> connected. After adding firewire_ohci to RTIRQ_NON_THREADED list and
> restarting rtirq the load dropped to something like 20%.

After asking around, I was unable to find any clues to your problems.
Don't have firewire myself, but I would think that the only file you
would possibly need to change is the rtirq script, and that is only if
it doesn't give higher prio to your firewire device.

To check prios, do: ps -eo comm,class,rtprio,ni,pri

The kernel is still a release candidate, so could be it has some problems.
Other than that, if no one here can help you, perhaps ffado would know
more about firewire specific issues.

> Xruns happen with a simple audio player (mocp), haven't tried anything
> heavyweight yet.
> Perhaps, some extra tweaking is required to enable this threaded irqs
> feature? Any suggestions? Thanks!
> --Artem


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