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Re: [Xen-devel] RT-Xen on ARM

On 03.07.17 21:42, Meng Xu wrote:
As far as I know, there is no known issue for ARM as long as that
version Xen runs on the ARM board.
 That's good.
I assume you have your own workloads to run, which are periodically
activated task.
The workloads in [1] are independent periodic CPU-intensive tasks: the
task does some computation for every period.
If your workloads are similar to the tasks, it should be ok.
Actually now we have just a high-level use case without any specific parameters defined. I.e. in an automotive system there should be a domain dedicated to instrumental cluster beside IVI domain. IC domain should be RT.
So we are just evaluating and experimenting with an existing functionality.

One thing in my mind that may affect your evaluations for your real
workload is what you want to achieve.

The RTDS uses the EDF scheduling, under which the priorities of the
VCPUs (or VMs) are dynamically changed based on their (absolute)
deadlines. This provides better real-time performance for the
*overall* system.
In case we would have a driver domain and IC domain would draw to pv display baked by backend in a driver domain. Driver domain should be RT capable as well.
So it seems two domains should be RT beside non-RT IVI domain.

If you want to make one VM highest priority and let that VM preempt
other VMs whenever the highest priority VM is active, it's better to
use the RM or FP scheduling, instead of the EDF scheduling.
So you are suggesting to introduce more RT schedulers with different algorithms. Did I get you right?

Once the scheduling policy is determined, you will need to configure
the VCPUs' parameters based on the systems' workload.
This requires the workload's timing parameters for the CARTS tool to
compute the VCPUs' parameters.
Thank you for suggestions.


*Andrii Anisov*

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