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I have tested Xen guest <-> guest communication on a single physical host using the latest Xen 3.5 unstable. I have a similar hardware configuration to what you have. I used the netperf to measure TCP and UDP throughput . I could achieve about 2.9Gbit/s between the two guests, and the results were stable. The guests were connected via a single bridge, and both were running PV guest kernels. What sort of kernel are you running, and what tool are you using to measure the throughput? Achieving only 10-40Mbit/s seems very low. How do you allocate your memory to the guests/Dom0? Have you also measure CPU utilization? What does it show? Are you also using iptables/ebtables or some sort of packet filtering in Dom0? What Xen version are you using?

From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Fasiha Ashraf
Sent: 30 June 2009 08:34
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Xen-bridge throughput

Hi there,
I have setup Debian etch host with 4 etch and 4 lenny guests on one of my servers.
Dell PowerEdge 2970:

2 x AMD Dual Core Opteron processors, 2GHz, 2 MB L2 Cache.
8 GB RAM (4 x 2 GB)
4 x 146 GB Hard Disks
Dual Port Gigabit Ethernet NIC
10 Gbps PCI Ethernet

I am performing different experiments for network throughput analysis of virtual bridge. For this purpose I am using a network benchmark. Most of the results are comparable to the other plate forms like fedora8 except one. That is While sending packets from Guest1 to Gueat2 on the same physical machine the throughput varies from 10 to 40 Mbps. But on 5th, 6th turn it increases all of a sudden with no change in specifications. It reaches almost 1800Mbps.
What could be the reason for it? Here is one more thing that I observed about it, the throughput is ok (around 1000 to 3000 Mbps) if the UDP is used instead of TCP. And even if we talk about Guest to Guest communication on different physical machines.
Why is that so... What is the cause of this variation in network throughput?

Regards,
Fasiha Ashraf

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RE: [Xen-users] Xen-bridge throughput