Re: [PATCH 5/5] sched/arinc653: Implement CAST-32A multicore scheduling

[Dario Faggioli <dfaggioli@xxxxxxxx>]

On Thu, 2020-09-17 at 15:10 +0000, Stewart Hildebrand wrote:
> On Thursday, September 17, 2020 5:04 AM, Jürgen Groß wrote:
> > On 16.09.20 20:18, Jeff Kubascik wrote:
> > > This change is an overhaul of the ARINC653 scheduler to enable
> > > CAST-32A
> > > multicore scheduling. CAST-32A specifies that only one partition
> > > (domain) can run during a minor frame, but that domain is now
> > > allowed to
> > > have more than one vCPU.
> > 
> > It might be worth to consider using just the core scheduling
> > framework
> > in order to achive this. Using a sched_granularity with the number
> > of
> > cpus in the cpupool running ARINC653 scheduler should already do
> > the
> > trick. There should be no further midification of ARINC653
> > scheduler
> > required.
> > 
> 
> This CAST-32A multicore patch series allows you to have a different
> number of vCPUs (UNITs, I guess) assigned to domUs. 
>
Yep, you can have domains with different numbers of vCPUs, when using
core-scheduling (or socket-scheduling, or ...), if this is what you're
asking.

> For example, dom1 has a single vCPU, and dom2 has 4 vCPUs. I didn't
> think the core scheduling framework had this flexibility?
>
It does.

And if you have domain A with 1 vCPU and domain B with 2 vCPUs, with
sched-gran=core:
- when the vCPU of domain A is scheduled on a pCPU of a core, no vCPU 
  from domain B can be scheduled on the same core;
- when one of the vCPUs of domain B is scheduled on a pCPU of a core, 
  no other vCPUs, except the other vCPU of domain B can run on the 
  same core.

With sched-gran=socket, the same, with s/core/socket. :-)

So indeed it seems that sched-gran=NR_CPUS (actually, number of CPUs in
the pool, as Juergen is saying) may indeed do what you want.

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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