Re: RT-Xen on ARM

[Andrii Anisov <andrii_anisov@epam.com>]

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.

[1] https://www.cis.upenn.edu/~linhphan/papers/emsoft14-rt-xen.pdf

> The configuration for the VCPUs depends on the tasks and the OS
> scheduler running on the VCPUs.
> The VCPU's utilization (budget/period) is usually larger than the
> tasks' utilizations (\sum e_i / p_i), where e_i is the task's
> worst-case execution time, and p_i is the task's period.
> The VCPU's parameters can be calculated by the CARTS tool [1],
>
> [1] https://rtg.cis.upenn.edu/carts/index.php
Got it.

> Did you try "sudo xl top"?
> IIRC, sudo xl top should work.
It was an issue of our yocto build. Xentop was not installed.
>> - root@salvator-x-h3-xt:/scripts# xl sched-rtds -d DomU -v all -p 10000 -b 2500
>>    (XEN) FLASK: Denying unknown domctl_scheduler_op: 2.
>>    libxl: error: libxl_sched.c:663:sched_rtds_vcpu_set_all: Domain 2:Setting vcpu sched rtds: Operation not permitted
>>    libxl_vcpu_sched_params_set_all failed.
> Which version of Xen or commit point did you use?
We have our stuff based on top of 4.9.0-rc6.

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*Andrii Anisov*

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