Re: RT task scheduling

[Ingo Molnar <mingo@elte.hu>]

* Bill Huey <billh@gnuppy.monkey.org> wrote:

> On Fri, Apr 07, 2006 at 09:11:25AM +0200, Ingo Molnar wrote:
> > * Bill Huey <billh@gnuppy.monkey.org> wrote:
> > 
> > > On Thu, Apr 06, 2006 at 09:37:53AM +0200, Ingo Molnar wrote:
> > > > do "global" decisions for what RT tasks to run on which CPU. To put even 
> > > > less overhead on the mainstream kernel, i plan to introduce a new 
> > > > SCHED_FIFO_GLOBAL scheduling policy to trigger this behavior. [it doesnt 
> > > > make much sense to extend SCHED_RR in that direction.]
> > > 
> > > You should consider for a moment to allow for the binding of a thread 
> > > to a CPU to determine the behavior of a SCHED_FIFO class task instead 
> > > of creating a new run category. [...]
> > 
> > That is already possible and has been possible for years.
> 
> I know that this is already the case. What I'm saying is that the 
> creation of new globally scheduled run case isn't necessarly if you 
> have a robust thread to CPU binding mechanism, [...]

-ENOPARSE. CPU binding brings with itself obvious disadvantages that 
some applications are not ready to pay. CPU binding restricts the 
scheduler from achieving best resource utilization. That may be fine for 
some applications, but is not good enough for a good number of 
applications. So in no way can any 'CPU binding mechanism' (which 
already exists in multiple forms) replace the need and desire for a 
globally scheduled class of RT tasks.

> [...] the key here is "robust". [...]

-ENOPARSE. CPU binding is CPU binding. Could you outline an example of a 
"non-robust" CPU binding solution?

	Ingo