Re: [RFC] Scheduler issue 1, RT tasks ...

[Mike Kravetz]

On Fri, Dec 21, 2001 at 09:19:04AM -0800, Davide Libenzi wrote:
> On Fri, 21 Dec 2001, Mike Kravetz wrote:
> 
> > Some time back, I asked if anyone had any RT benchmarks and got
> > little response.  Performance (latency) degradation for RT tasks
> > while implementing new schedulers was my concern.  Does anyone
> > have ideas about how we should measure/benchmark this?  My
> > 'solution' at the time was to take a scheduler heavy benchmark
> > like reflex, and simply make all the tasks RT.  This wasn't very
> > 'real world', but at least it did allow me to compare scheduler
> > overhead in the RT paths of various scheduler implementations.
> 
> Mike, a better real world test would be to have a variable system runqueue
> load with the wakeup of an rt task and measuring the latency of the rt
> task under various loads.
> This can be easily implemented with cpuhog ( that load the runqueue ) plus
> the LatSched ( scheduler latency sampler ) that will measure the exact
> latency in CPU cycles.

Right!  Any ideas on variable system runqueue load?  Should those
other tasks be RT or OTHER? a mix?  I would suspect that we would
want multiple RT tasks on the runqueue or at least in the system
(otherwise why worry about global semantics?).

However, I would feel better about this if someone had a real world
load involving RT tasks on a SMP system.  At least then we could try
to simulate a load someone cares about.

-- 
Mike