Re: [PATCH]sched: Isochronous class v2 for unprivileged soft rt scheduling

[Jack O'Quin]

"Rui Nuno Capela" <rncbc@xxxxxxxxx> writes:

> OK. Here goes my fresh and newly jack_test4.1 test suite. It might be
> still rough, as usual ;)

Thanks for all your work on this fine test suite.

> This phenomenon, so to speak, shows up as a sudden full increase of
> DSP/CPU load after a few minutes running jackd while perfectly normal and
> stable until that moment. Once that occurs, and it does now everytime I
> run jack_test4_run.sh with default parameters (14 clients, 4x4 ports), you
> end under a horrible XRUN storm--see attached chart--you can even hear it
> perfectly as the 1KHz audible tone burps and stutters, resembling
> radioactivity morse pulses.

Looking at the graph, it appears that your DSP load is hovering just
above 70% most of the time.  This happens to be the default threshold
for revoking realtime privileges.  Perhaps that is the problem.  Try
running it with the threshold set to 90%.  (I don't recall exactly
how, but I think there's a /proc/sys/kernel control somewhere.)

> So it seems that this showstopper is an issue only under extreme loads,
> and is probably relative to the hardware you're running into. On my other
> P4@xxxxxx/HT desktop I could not reproduce this. Instead, I hit a rather
> older issue, which comes like the magic 14 client limit. As it seems, I
> now find trouble when starting more than 14 connected clients, as the
> jack_watchdog kills everything in sight beyhond that point. This wasn't
> happening with the jack_test3.2 suite, suspectedly because those clients
> weren't being connected to each other.

I'll take a look.  The old problem with more than 14 clients has been
fixed.  I routinely run 30 or 40 without trouble.  

Perhaps we're running out of some port resource?

> Please check this out, and would you try at least to reproduce the naughty
> behavior such as the pictured on the attached chart?

Will do.
-- 
  joq
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