Re: RT-Xen on ARM

From: Andrii Anisov <andrii_anisov@epam.com>
To: Meng Xu <xumengpanda@gmail.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: RT-Xen on ARM
Date: Tue, 4 Jul 2017 15:28:48 +0300	[thread overview]
Message-ID: <88185ae6-d1cf-898c-fe18-a569b0049230@epam.com> (raw)
In-Reply-To: <CAENZ-+=syCWWSc+vGP-9FbLeULYXncZT6Qj64AEPv8NWRDMqTg@mail.gmail.com>


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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