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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Jul 30, 2013 at 11:00:20AM -0400, Shakeel Butt wrote:
> On Tue, Jul 30, 2013 at 9:39 AM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> > 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.
> 
> Thanks. Is there one kthread for each netback/netfront pair or is there one
> kthread for each domain?
> 

One kthread for each driver domain CPU. Each Vif is statically assigned to a
specific kthread.


Wei.

> Shakeel
> 
> >
> >
> > Wei.
> >
> >> thanks,
> >> Shakeel
> >>
> >> _______________________________________________
> >> Xen-devel mailing list
> >> Xen-devel@xxxxxxxxxxxxx
> >> http://lists.xen.org/xen-devel

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