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

[Con Kolivas <kernel@kolivas.org>]

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Cal wrote:
> Con Kolivas wrote:
> 
>> Comments and testing welcome.
> 
> 
> There's a collection of test summaries from jack_test3.2 runs at
> <http://www.graggrag.com/ck-tests/ck-tests-0501182249.txt>
> 
> Tests were run with iso_cpu at 70, 90, 99, 100, each test was run twice. 
> The discrepancies between consecutive runs (with same parameters) is 
> puzzling.  Also recorded were tests with SCHED_FIFO and SCHED_RR.
> 
> Before drawing any hardball conclusions, verification of the results 
> would be nice. At first glance, it does seem that we still have that 
> fateful gap between "harm minimisation" (policy) and "zero tolerance" 
> (audio reality requirement).

Thanks.

SCHED_ISO
/proc/sys/kernel/iso_cpu . . .: 70
/proc/sys/kernel/iso_period . : 5
XRUN Count  . . . . . . . . . :   110

vs

SCHED_FIFO
XRUN Count  . . . . . . . . . :   114
XRUN Count  . . . . . . . . . :   187

vs

SCHED_RR
XRUN Count  . . . . . . . . . :     0
XRUN Count  . . . . . . . . . :     0

Something funny going on here... You had more xruns with SCHED_FIFO than 
the default SCHED_ISO settings, and had none with SCHED_RR. Even in the 
absence of the SCHED_ISO results, the other results dont make a lot of 
sense.

Con

P.S. If you're running on SMP it may be worth booting on UP or using cpu 
affinity (schedtool -a 0x1 will bind you to 1st cpu only) and see what 
effect that is having. There are some interesting things that can 
adversely affect latency on SMP.

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