Doubts about Kvm architecture

Doubts about Kvm architecture

[Maurício Almeida]

Hello Guys!
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?

Thank you
Att Maurício Almeida

Re: 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

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