Re: [Xen-users] priority of dom0?

[Sven Köhler <skoehler@xxxxxx>]

>>>> when i compile something in dom0, my domUs are more then 
>>>> unresponsible.
>>>> Any clue, what's going on? How can i change the "priority" 
>> of dom0? I
>>>> think, that the CPU-time should be equally distributed 
>>>> between the dom0
>>>> and the domUs.
>>> Whilst you can do this, the risk is that you get other 
>> problems if you do that (like one DomU running away and Dom0 
>> not getting a chance to run instead :-( which is slightly 
>> worse, in case you would like to for example KILL that 
>> DomU!)...  You also want Dom0 to have a high priority (or to 
>> be able to run for as long as it needs) to be able to 
>> correctly and quickly respond to IO requests made on behalf 
>> of DomU's. Unfortunately, this counteracts the Dom0 being low 
>> priority...
>>
>> Well, i would expect some "fairness", that is:
>>
>>   50% dom0, 50% domU
>> or
>>   33% dom0 and 66% for two domUs
>> or
>>   25% dom0 and 75% for three domUs
>> and so on ...
>>
>> Perhaps, people would also like to say: guarantee up to 33% 
>> percent CPU
>> usage to dom0. (Not meaning, that dom0 is limited to 33% and 
>> not meaning
>> that all domUs together are limited to 66%)
>>
>> Don't you think, that this would be enough to ensure that IO 
>> and network
>> is working properly?
>>
>> Of course, that requires a (fairly simple?) scheduler within Xen.
> 
> That is what the credit scheduler is supposed to do... What version of Xen 
> are you using?
> 
> What does it say if you do "xm dmesg | grep -i sched"?

I am using Xen 3.0.2. I seem to be using the sedf scheduler. I didn't
change anything concerning the scheduling. I'm using the default.
Here is the state of my current configuration:

# xm dmesg|grep -i version
 Xen version 3.0.2 (root@(none)) (gcc-Version 4.1.1 (Gentoo 4.1.1)) Fr
Okt  6 22:52:03 Local time zone must be set--see zic manual page 2006

# xm dmesg|grep -i sched
(XEN) Using scheduler: Simple EDF Scheduler (sedf)

# xm sched-sedf
Name                    ID Period(ms) Slice(ms) Lat(ms) Extra Weight
Domain-0                 0      20.0      15.0     0.0      1      0
xen-sk1                  3     100.0       0.0     0.0      1      0
xen-to1                  2     100.0       0.0     0.0      1      0


I'm searching for documentation about the scheduler and their
parameters. I didn't find much.

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