[linux-audio-dev] Re: [Jackit-devel] [REQUEST] test the influence of linux1394 kernel drivers on scheduling latency

Pieter Palmers pieterp at joow.be
Wed Jun 21 08:42:18 UTC 2006


Lee Revell wrote:

>On Wed, 2006-06-21 at 00:21 +0200, Pieter Palmers wrote:
>  
>
>>Hi all,
>>
>>This weekend I've discovered a (serious) kernel scheduling latency issue 
>>with the current ieee1394 kernel drivers. Before I submit something 
>>about this to lkml, I'd like some more tests. I've been able to 
>>reproduce this on two different machines, so I suspect that this is a 
>>more general problem.
>>
>>The problem summary is that running ieee1394 ISO traffic can cause 
>>scheduling latency spikes up to 1ms, even for RT threads with higher 
>>priority.
>>
>>    
>>
>
>Latency tracer output please?
>
>Use 2.6.16 with this patch:
>
>http://people.redhat.com/mingo/latency-tracing-patches/latency-tracing-v2.6.16.patch
>
>  
>
I've tried using the latency tracer, but I was unable to get any other 
results than the system timer (or what extactly was it called) at about 
20us. Nothing from the ieee1394 stack showed up.

I probably need some usage explanation because the stuff I find googling 
around seems to be out of date. Or at least it does not provide the info 
I need to get usefull output. But that could be me.

Greets,

Pieter

BTW: should you have a firewire card, try it for yourself. After all, 
that saves you the explanation, and I'm pretty confident that it will be 
present on other machines too.



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