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

On Mon, Jul 3, 2017 at 7:03 AM, Andrii Anisov <andrii_anisov@xxxxxxxx> wrote:
> Dear Meng Xu,

Hi Andrii,
> We are going to evaluate an RTDS scheduler on ARM.
> Basically I'm going to repeat use-cases described in 
> https://www.cis.upenn.edu/~linhphan/papers/emsoft14-rt-xen.pdf in some amount.

I see. Please don't hesitate to ask if you have any question about the results.

> 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?

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

> BTW, even following 
> https://xenbits.xen.org/docs/unstable/features/sched_rtds.html I've faced 
> several issues, not rtds one, but nasty:
> - no xentop for ARM

Did you try "sudo xl top"?
IIRC, sudo xl top should work.
> - 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?



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

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