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RE: [Xen-users] Xen Performance

<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>

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.  Here is why:

Between domU A and domU B, the traffic has to traverse domU A's vif in dom0, 
the bridge in dom0, and domU B's vif in dom0.  That is three virtual devices.

Between domU A and dom0, the traffic only has to traverse domU A's vif and the 
bridge, it has then arrived in dom0, that is only two virtual devices.

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.  Regarding the performance 
difference, my opinion is that we could always use more performance in all 
aspects, period.  Sure, eventually costs are prohibiting and we have to settle, 
but more performance wouldn't hurt no matter how many people think performance 
is good enough, and only seeing notably better performance can convince some 
people that any given performance isn't good enough.


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