>> I can't understand this as disk activity should be running on cores 0,
>> 1 and 2, but never on core 3. The only thing running on core 3 should
>> by my paravirtual machine and the hypervisor stub.
>>
>> Any idea what's going on?
Your Core i3 is a Dual Core Processor with Hyper Threading. Hyper Threading allows each Core to run two Threads simultaneously, in what is called physical Core and virtual Core (Or around those lines, but you get the idea). They share resources, and the extra Thread actually gets the free resources/execution time that weren't used by the main Thread. As Core 3 is the virtual core of the physical Core 2 (Assuming that on Linux it sees and numbers them as Physical Core 0, Logical Core 1, Physical Core 2 and Logical Core 3 and so on), you're giving that VM just a spare virtual Core with the free resources that weren't used by the physical Core. You should try with a full physical Core (Core 2 and 3), otherwise whatever runs on Core 2 WILL impact heavily what you see on Core 3.
