[LAU] rtirq - what does it improve, and how can I measure it?

[Kaj Ailomaa]

On 05/07/2012 02:24 PM, Jeremy Jongepier wrote:
> On 05/07/12 14:06, Kaj Ailomaa wrote:
>> I understand that the rtirq script is designed to raise rtprio for audio
>> devices, which is made possible on the vanilla kernel since 2.6.39(?),
>> if passing the threadirqs option to the kernel at boot, and having built
>> it with the CONFIG_FORCE_THREADIRQ.
>>
>> From my experience, I have not had any performance boost using the
>> rtirq script, but I have read about it helping those who are getting
>> xruns due to irq sharing.
>>
>
> Hello Kaj,
>
> rtirq allows you to elevate the prios of softirq's which could enhance
> the performance of those prioritized softirq's. So it doesn't really
> boost the overall performance of a system.
>
>> So, I'm wondering. What picture do others have of the benefit of the
>> rtirq script?
>>
>
> Without rtirq I simply can't use my FireWire card on my notebook for
> example. The FireWire controller shares its IRQ with a plethora of other
> devices (GPU, WiFi, cardreader) and if I don't use rtirq jackd simply
> won't start.

Does anyone ever find themselves not being able to solve their problem 
with the rtirq script?
And what about software processes? The network-manager, cron, and other 
things we have heard about, when you get periodic xruns no matter which 
latency you use. Can we make all of those problems go away by changing 
rtprio for devices?

>
>> ..and are there other ways to measure improvement for audio operation
>> other than spotting xruns at different latency settings, and reading the
>> rtprio for various devices using the 'ps' command?
>
> Yes, htop and latencytop for example.
>
> Best,
>
> Jeremy
>
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