Re: rtirq - what does it improve, and how can I measure it?

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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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