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

[Meng Xu <xumengpanda@xxxxxxxxx>]

On Tue, Oct 18, 2016 at 6:51 AM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> CC Dario and Meng

Thank you very much for cc.ing me, Wei! :-)

>
> On Mon, Oct 17, 2016 at 10:55:21PM +0100, Juergen Schinker wrote:
>> Hey Meng XU

Hi,

Thanks for your interest in RTDS scheduler! :-)

>>
>>
>> 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

I guess you used xl sched-rtds to show the paramters.
The "xl sched-rtds" is a legacy command. It is supposed to show the
period and budget of *all* VCPUs of the same domain.  In Xen 4.5, RTDS
scheduler only allows setting same period and budget for *all* VCPUs
of the same domain.
In Xen 4.7, RTDS scheduler allows setting individual period and budget
for each VCPU of the same domain. Then "xl sched-rtds" won't make
sense because VCPUs have different periods and budgets.

The short story is:
If you use "xl sched-rtds -v all", you will see the parameters are changed.

Another thing is that the current RTDS scheduler will only allocate
the amount of resource to the VCPU you set.  Since you set period and
budget to be 20000 and 8000, you only get 40% CPU resource. (We won't
get more resource than you set under the current RTDS.)

We are working on another improved version of the RTDS, which could
let a VCPU get more resource that specified when there is idle
resource left in the system.
If you could tell us what you want to use RTDS to achieve, we could
take that into consideration when we improve the RTDS further.

Thanks,

Meng

-----------
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/

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