Re: [Xen-devel] CPU utilization

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

The default BVT scheduler is weighted fair share with extensions to 
better support I/O. If you add extra domains then the existing ones 
will get proportionally less CPU, assuming all domains are CPU bound.
More directly answering your question: most sane CPU schedulers are 
work conserving, meaning that if there is work to be done then they 
will schedule it in preference to idling. This means that if, say, 
domain0 is the only domain with work to do then it will get 100% of the 
CPU, even if its 'fair share' is, say, 50%. Now, however strict you are 
in scheduling a runnable domU onto the same processor it is clearly 
going to have some negative impact on domain0's CPU allocation compared 
with dom0 getting all the CPU.
 -- Keir

On 1 May 2005, at 14:51, Brian Hays wrote:

> A question about CPU utilization...
>
> If I have a domU that is under heavy processing load will it affect
> the performance of other domU's or dom0? ...or is processing divided
> in such a way that one domU will have no effect on others no matter
> what load it is under?
>
> Thank you,
> Brian
>
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