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

On Mon, Jul 3, 2017 at 10:58 AM, Andrii Anisov <andrii_anisov@xxxxxxxx> wrote:
> Hello Meng Xu,
> On 03.07.17 16:35, Meng Xu wrote:
>>> Do you have any recommendations or suggestions?
>> Which experiment/use case do you plan to run?
>> What are the requirements (or performance guarantees) you want to have
>> from RTDS?
> Currently we have no defined target use-cases.
> That's why we are going to keep configuration (of guests and workloads)
> close to [1] for evaluation, but on our target SoC.
> I'm wondering if there are known issues or specifics for ARM.

As far as I know, there is no known issue for ARM as long as that
version Xen runs on the ARM board.

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.

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.
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.

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.



Meng Xu
PhD Candidate in Computer and Information Science
University of Pennsylvania

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