Apple

On 1 Jun 2016, at 10:00, Julian Dessecker <email@hidden> wrote:

> Tim,
>
> thanks for that information. I had a look at the xnu source - you are right. The constraint won't prevent a real-time thread from starving non-realtime threads.
>
> Julian
>
> On Tue, May 31, 2016 at 9:51 PM, Tim Hewett <email@hidden> wrote:
> Julian,
>
> The constraints parameters were ignored in the kernel for many generations of OS X in spite of the documentation defining their use. The real documentation (the source code) said otherwise.
>
> I am not sure if they are still ignored, IIRC the kernel-side code is not hard to find to check.
>
> Tim.
>
>
> On 31 May 2016, at 20:00, email@hidden wrote:
>
> > Hi,
> >
> > I'm trying to create real-time threads via the
> > THREAD_TIME_CONSTRAINT_POLICY.
> > It works fine, an interrupt after each computation cycle can be seen inside
> > the profiler (Instruments / System Trace) but the constraint seems to be
> > ignored.
> >
> > I would expect a penalty after the constraint time is over but the thread
> > stays on the CPU starving other threads.
> >
> > That's the way I initialize the time constraint policy:
> >
> > thread_time_constraint_policy_data_t time_constraints;
> >
> > time_constraints.period = (int) NanosecondsToAbsolute (1000000); // 1
> > ms
> >
> > time_constraints.computation = (int) NanosecondsToAbsolute (250000); //
> > 0.25 ms
> >
> > time_constraints.constraint = (int) NanosecondsToAbsolute(500000); //
> > 0.5 ms
> >
> > time_constraints.preemptible = 1;
> >
> > thread_policy_set(mach_thread_self (), THREAD_TIME_CONSTRAINT_POLICY,
> > (thread_policy_t) &time_constraints, THREAD_TIME_CONSTRAINT_POLICY_COUNT);
> >
> > Any ideas how to get the constraint working?
> >
> > Regards,
> > Julian
>
>

References:
	>Re: Time constraint real-time threads (From: Julian Dessecker <email@hidden>)
	>Re: Time constraint real-time threads (From: Tim Hewett <email@hidden>)