Re: [Xen-devel] xen 4.5.0 rtds scheduler perform poorly with 2vms

[Lars Kurth <lars.kurth.xen@xxxxxxxxx>]

I wonder whether we need to add some health warnings and recommended background 
reading to http://wiki.xenproject.org/wiki/RTDS-Based-Scheduler
Lars

> On 1 Dec 2015, at 08:59, Dario Faggioli <dario.faggioli@xxxxxxxxxx> wrote:
> 
> On Sun, 2015-11-29 at 11:44 -0500, Meng Xu wrote:
>> 2015-11-29 11:27 GMT-05:00 Dario Faggioli <dario.faggioli@xxxxxxxxxx>
>> :
>>>  
>>> Mmmm... As I said many times, I don't remember much of all those RT
>>> schedulability formulas, but, is really that simple?
>> 
>> Ah, let me clarify...
>> It is not that simple. ;-) I just simplify it, hoping it can simplify
>> the problem and highlight the possible reason.
>> 
> Ok, glad to know I haven't completely lost my mind, or anything like
> that! :-)
> 
>>> I mean, if the in-
>>> guest scheduling algorithm is global (e.g., global-EDF), the task
>>> could
>>> migrate, couldn't it?
>> 
>> Yes. If these partial VCPUs happen to be scheduled "sequentially",
>> the
>> OS inside VM can migrate the task and make the task keep running. But
>> that is not the worst-case for the OS.
>> 
> Right, I see it now, and (FWIW) I absolutely agree with the worst-case
> analysis you provided (thanks). I did not get the fact that you were
> talking about the worst-case, sorry for the noise. :-D
> 
>> The detailed illustration of the worst case scenario is at Arvind's
>> paper: http://link.springer.com/article/10.1007%2Fs11241-009-9073-x
>> My latest journal paper
>> (http://link.springer.com/article/10.1007%2Fs11241-015-9223-2)
>> tighten
>> the resource supply bound function of the MPR model. I believe the
>> equations are too boring to most of people in the mailing list.
>> 
>> So let's avoid the complex equations here. ;-)
>> 
> Thanks for this too! :-)
> 
> 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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