Re: Time constraint real-time threads
Re: Time constraint real-time threads
- Subject: Re: Time constraint real-time threads
- From: Tim Hewett <email@hidden>
- Date: Tue, 31 May 2016 20:51:55 +0100
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
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