Re: RT-Xen on ARM

From: Dario Faggioli <dario.faggioli@citrix.com>
To: Andrii Anisov <andrii_anisov@epam.com>, Meng Xu <xumengpanda@gmail.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: RT-Xen on ARM
Date: Wed, 5 Jul 2017 10:42:57 +0200	[thread overview]
Message-ID: <1499244177.7486.7.camel@citrix.com> (raw)
In-Reply-To: <88185ae6-d1cf-898c-fe18-a569b0049230@epam.com>

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On Tue, 2017-07-04 at 15:28 +0300, Andrii Anisov wrote:
> On 03.07.17 21:42, Meng Xu wrote:
> > 
> > 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.
> 
Currently (and this is not changing anytime soon), the only way of
using different schedulers for different domains is by means of
cpupools.

I.e., you create, for instance, an RTDS pool, and a Credit or Credit2
pool. In the RTDS pool, you put the RT domains, so the IC domain and
the driver domains, and you subdivide resources between them according
to the utilization and latency requirements that each one of them has.

You then put all the non-RT domains in the other pool, and you control
their behavior via weighs, cap, pinning (etc).

Of course, this is just an example, and whether or not it is the best
way of going, as well as the specific parameters, really depends on the
characteristics of your platform and of your workload.

Trying to reason on as detailed as possible scenario, and then actually
testing and benchmarking every envisioned solution, is the only way to
actually tell what will work best.

As I said in the other email, I'm more than up discussing this, either
via email or in person (e.g., at the Summit).

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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