[LITMUS^RT] Unexpected worst case response time

[Junjie Shi]

Hello,

Yes, I used 'rtspin' to allocate the task. And what I expect is the WCRT =
execution time + overheads, 0.3 ms overheads for DPCP is too large to be
accepted. I will turn off all the debugging options and try that again.
Thank you very much!

Best wishes!
SHI

2017-03-28 14:23 GMT+02:00 Björn Brandenburg <bbb at mpi-sws.org>:

>
> > On 28 Mar 2017, at 12:14, 施俊杰 <shijunjie92 at gmail.com> wrote:
> >
> > I got some unexpected results during my experiments when using the
> protocol under P-FP plugin. I used 'rtspin' to set the task,
> 'st-trace-schedule' to collect the data and 'st-job-stats' to handle the
> data.
>
> What does the schedule look like?
>
> > I set my task as follows: WCET: 1ms, critical section: 0.5 ms,
> partition: cpu_0, resource location: cpu_1, protocol: DPCP, period: 2ms,
> total execution time: 100s.
>
> Is this using rtspin?
>
> > There is only one real-time task in my system. The result of the WCRT is
> 1.34 ms which is too large than the expected value.
>
> What response time did you expect? Keep in mind that the task still needs
> to do some other work to prepare the next periodic release.
>
> > And if I set the protocol as MPCP, partition is cpu_0 (same as resource
> location), the WCRT is 1.125 ms, which is also too large.
>
> Again, what did you expect?
>
> > Moreover, if I add the number of tasks to 40, the unexpected overheads
> of DPCP can be accumulated to more than 1 ms.
> > Can any one explain that?
>
> Can you trace the source of the overhead?
>
>
> > Or do I need to modify my configuration?
>
> Depends on what you have enabled… did you turn off all debugging options?
>
> - Björn
>
>
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-- 
Best wishes!
SHI
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