Re: [Xen-devel] Bidirectional network throughput for netback

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Jul 30, 2013 at 02:39:50AM -0400, Shakeel Butt wrote:
> Hi,
> 
> Is there any limitation on the bidirectional throughput of netback
> driver? Measuring the inward and outward traffic throughput of a DomU
> in parallel effects both flows. Let me explain my experiment setup for
> better understanding.
> 
> In my experiments I have three machines i.e. A, B and C, equipped with
> Xen 4.3 and Linux 3.6.11 and configured with 2vcpus & 2GB RAM. I am
> running DomU on machine 'B' having same configuration(3.6.11, 2vcpus &
> 2 GB). I am measuring the network throughput between DomU and machine
> 'A' and 'C' (or Dom0 on those machines). The traffic is generated from
> A to DomU and from DomU to C. If I generate only one traffic flow at a
> time, I get similar throughput for both flows, lets say X Mbps but if
> I generate traffic in parallel, X is divided in between these two
> flows. Now in the experiment if I change DomU to Dom0 of 'B'
> (basically no netback usage in B) I get X throughput for both traffic
> flows even if I generate traffic in parallel. So, it seems to me that
> 'netback' for DomU is the bottleneck. Is this right? If so what design
> choice in netback is causing this issue?
> 

Currently there is only one kthread in netback for DomU's transmit and
receive queues, so it is normal to see the throughput drops to half.


Wei.

> thanks,
> Shakeel
> 
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