Re: [Qemu-devel] Doubts about Kvm architecture

[Mihai Donțu]

On Wed, 2017-05-31 at 14:09 -0300, Maurício Almeida wrote:
> My name is Maurício, we are making a study about Kvm Paravirtualized
> and Full virtualized at our University, we are from University Federal
> of Santa Maria.
> Can you give us some papers about how the Kvm or Qemu executes the I/O
> Network with one emulated Device?
> 
> We executed some tests using Virtio Driver and e1000 emulated driver,
> the network output of Virtio is normal and use four of the four
> Machine Cpu's, but the output of e1000 Emulated driver was too low
> about Virtio and It onlyused one of the four machine cpu's during the
> network test execution.
> The Traffic of Virtio was 956 MB/s while e1000 Emulated Driver was 192
> MB/s, both using Packet size of 1518 Bytes.
> 
> Why when it used e1000 Emulated Driver the traffic was to low and use
> only one Cpu all the time?
> Do Qemu or Kvm Guest need some specific configuration to use all CPU's?
> 
> Do you have any paper where we can find in details if Qemu is limited
> to use one CPU when use Network Emulated Driver?

A cursory look over the qemu e1000 driver would suggest that it does
not support multithreading. virtio largely bypasses the qemu hw
machinery.

-- 
Mihai Donțu