[LAU] rt kernel in debian/squeeze

Jörn Nettingsmeier nettings at folkwang-hochschule.de
Mon Jan 10 09:43:04 UTC 2011


On 01/08/2011 03:55 PM, Robin Gareus wrote:
> On 01/08/2011 03:16 PM, Bernardo Barros wrote:
>> ondemand is no good because when it switches the processor actually
>> stops for a very short time. but this short drops are enough to cause
>> the terrible xruns on jack. stick to performance or conservative :-)
>
> I'm tempted to call BS.
>
> I can't find a reference or link but IIRC the "short time" a processor
> stalls when changing frequency is these days in the usec range.
>
> Anyway, discard all theory. It works empirically:
> There are no problems here with JACK at 32*2 fpp @48kHz with the
> ondemand govenour on both Intel Core Duo, Intel Core 2 Duo and Intel i5
> CPUs (yes, that is going from nought to 16 jconvolvers causing CPU and
> JACK load to jump).

anecdotal evidence: on my system(s), using ondemand is absolutely deadly 
when using the ffado backend.

with the alsa backend, the system is mostly ok when running ondemand, 
but then again i run fairly high latencies because jconvolver gets 
really expensive when you shrink the period size...


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