Implement THREAD_PRIORITY_TIME_CRITICAL

[Andreas Mohr]

Hi,

On Tue, Apr 04, 2006 at 03:49:56PM +0100, Mike Hearn wrote:
> So in this case either the CPU time goes way high when the 3D scene 
> first appears, or maybe my 3D driver (nvidia) is not allowing 
> pre-emption enough.

nvidia... nvidia... Hrmmm... might this just be caused by the recent
annoying sched_yield nvidia driver issue that also managed to char-coal
Xgl completely? (jagged window moves, abysmal performance, ...)?

Just a stab in the dark, but...

> I guess I'm uneasy about this idea of keeping cpu time low, even for 
> threads we control, because how do we debug it? How does one monitor a 
> scheduler anyway? Maybe the problem is our audio thread is using too 
> much cpu time - ok, how do we measure that? How much is too much? What 
> threshold do we have to beat to get scheduling latency low enough to 
> work properly? How do we figure out if the scheduler is doing what we 
> think it's doing? What if it is a driver problem? This all seems very 
> opaque to me.

Exactly my thoughts. Debugging it may be somewhat difficult, but if it
finally works then a non-realtime solution (whatever the problem actually is)
will be so much nicer from a clean design point of view.

Andreas