Re: [Xen-users] vCPUs and Weight/Caps

[Peter Viskup <skupko.sk@xxxxxxxxx>]

On 01/09/2013 07:30 PM, mohammed.king@xxxxxxxxx wrote:
> Hello Everyone,
>
> I am hoping I can get some help with how vCPUs work with weights and caps
>
> 1. If I have a domU with 2 vCPUs and a weight of 256, does the weight double 
> (512) or is this 256 time slice across both vCPUs. If the weight does not 
> double, how is it beneficial to have multiple vCPUs?
>
> 2. If the domU has 2vCPUs and a cap  of 100% how does this work since 100% is a 
> mex of one physical CPU.
>
> Thanks,
> Mohamed
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> http://lists.xen.org/xen-users
Hi Mohammed,
both of these are related to Credit scheduler [1].
Weight is domain attribute (not vCPU) and the benefit of this is to 
effectively distribute the CPU time between the domains. The domain with 
higher weight has better chance to get CPU time.
The cap is the maximum of CPU the domain can have available.
Read the "Algorithm" section on that wiki and everything will be clear 
for you. It's always better to read some documentation before asking 
such questions. ;-)
[1] http://wiki.xen.org/wiki/Credit_Scheduler

BR,
--
Peter Viskup

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