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Re: [Xen-users] Xen Performance

On Fri, Oct 16, 2009 at 7:43 PM, Dustin Henning
<Dustin.Henning@xxxxxxxxxxx> wrote:
> <snip> DomU to DomU performance is 1/3 to 2/3 that of DomU to Dom0 even 
> though that the DomU to DomU traffic is probably traversing the same path as 
> DomU to Dom0. <snip>
> Cheers!
> Grant McWilliams
> ______________________________________
> Seeing as how each domU nic exists in dom0, as does the bridge, I would argue 
> that traffic between domU and domU take 50% more steps than traffic between 
> domU and dom0.  Looking at it the other way, that would be 33% less steps 
> between domU and dom0 than domU and domU.

It would make sense if domU <-> domU is SLOWER than dom0 -> domU ...
the thing is it's not the case :D

Grant seems to have other problems (broken pipe) in his domU <-> domU
test, so lets ignore that for now. My test case has shown that domU
<-> domU and domU -> dom0 got good results. Only dom0 -> domU is
considerably worse.

> I could be wrong, and would love to be given a more detailed and technical 
> answer as to how I am if that is the case.

That would be good, if one is available :) You might be able to get
better answer on xen-devel.

>  Regarding the performance difference, my opinion is that we could always use 
> more performance in all aspects, period.

Totally agree.

However, my point when replying to Igor's initial mail is that
considering all the requirements and limitations, bridged setup is
still on top of my list when choosing the "best" networking setup for
Xen. Even when dom0 -> domU is considerably slower.

Other setup (like pci passthrough for domU NIC) might be able to
provide better throughput, but it's too complicated for me (not to
mention that it prevents live migration from working). Then again,
what's best for me might not be the best for others, depending on
situation an priorities. YMMV.


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