[Xen-devel] Bidirectional network throughput for netback

[Shakeel Butt <shakeel.butt@xxxxxxxxx>]

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?

thanks,
Shakeel

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