Re: Priority Inheritance Test (Real-Time Preemption)

Ingo Molnar
2004-11-27T07:34:25Z

* Ingo Molnar <mingo@elte.hu> wrote:

>
> * Ingo Molnar <mingo@elte.hu> wrote:
>
> > the additional +1 msec comes from the fact that 1-deep lock/unlock of
> > lock1 is an allowed operation too - 2 msec would be the limit if the
> > only sequence is the 2-deep one.
> >
> > so i think the numbers, at least in the 2-deep case, are quite close
> > to the theoretical boundary.
>
> in the generic case i think the theoretical boundary should be something
> like:
>
> sum(i=1...n)(i) == (n+1) * n / 2
>
> n=1 limit=1
> n=2 limit=3
> n=3 limit=6
> n=4 limit=10
>
> this is quite close to what you have measured for n=1,2,3, and i think
> it's becoming exponentially harder to trigger the worst-case with higher
> N, so the measured results will likely be lower than that.

also, you might want to try the simpler N-deep-locking-only variant,
where the maximum latency should be 'n'. This likely needs some changes
to the blocker.c code though - i.e. set 'max' always to lock_depth.

Ingo