Re: [PATCH][RFC] sched: Isochronous class for unprivileged soft rt scheduling

[Con Kolivas <kernel@kolivas.org>]

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Jack O'Quin wrote:
> Con Kolivas <kernel@kolivas.org> writes:
> 
> 
>>This patch for 2.6.11-rc1 provides a method of providing real time
>>scheduling to unprivileged users which increasingly is desired for
>>multimedia workloads.
> 
> 
> I ran some jack_test3.2 runs with this, using all the default
> settings.  The results of three runs differ quite significantly for no
> obvious reason.  I can't figure out why the DSP load should vary so
> much.  
> 
> These may be bogus results.  It looks like a libjack bug sometimes
> causes clients to crash when deactivating.  I will investigate more
> tomorrow, and come up with a fix.
> 
> For comparison, I also made a couple of runs using the realtime-lsm to
> grant SCHED_FIFO privileges.  There was some variablility, but nowhere
> near as much (and no crashes).  I used schedtool to verify that the
> jackd threads actually have the expected scheduler type.

Thanks for those. If you don't know what to make of the dsp variation 
and the crashing then I'm not sure what I should make of it either. It's 
highly likely that my code still needs fixing to ensure it behaves as 
expected. Already one bug has been picked up in testing with respect to 
yield() so there may be others. By design, if you set iso_cpu to 100 it 
should be as good as SCHED_RR. If not, then the implementation is still 
buggy.

Cheers,
Con

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