Re: [Xen-devel] [BUG] XEN-4.8-rc2 sched-rtds does not accept settings

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Tue, 2016-10-18 at 11:51 +0100, Wei Liu wrote:
> CC Dario and Meng
> 
Hi,

Thanks Wei for the Cc...

> On Mon, Oct 17, 2016 at 10:55:21PM +0100, Juergen Schinker wrote:
> > 
> > xl -vf sched-rtds -v all -d 0 -p 20000 -b 8000
> > 
> > whatever I set - the changes are not accepted and stay like you see
> > further down
> > 
> > and the system feels very lame
> > 
> > Cpupool Pool-0: sched=RTDS
> > Name                                ID    Period    Budget
> > Domain-0                             0     10000      4000
> > zimbra                               1     10000      4000
> > ethereum-os                          2     10000      4000
> > mirot                                3     10000      4000
> > wily                                 4     10000      4000
> > 
Right, but what does the following shows:

 xl sched-rtds -d 0 -v all

?

On my system, just using `xl sched-rtds` as above also still shows the
4000/10000 budget over period pairs, but adding '-v all' shows the
correct (i.e., the new) parameters.

In fact, the two commands are basically showing different things. I
agree it's not really clear, and I'll think to ways of improving the
situation (e.g., by improving the documentation, but also by making the
`xl' interface more consistent).

About the 'system feels lame', what does that exactly mean? Actually,
what is it that you are trying to achieve by using RTDS?

RTDS is a special purpose scheduler, and should be chosen for the
proper reasons and configured accurately. Typical use case is need for
deterministic/real-time scheduling of VMs.

Oh, and also, default parameters are 4000/10000=40% utilization. By
setting them to 8000/20000=40%, you're not changing much, at least
nothing that will be noticeable as a 'general system feeling', because
all domains (well, each vCPU of each domain), including dom0 (dom0's
vCPUs), are still limited to use at most 40% of pCPU time --although
with different periodicity.

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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