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RE: [Xen-users] Xen-bridge throughput

To: AnnaFischer <anna.fischer@xxxxxx>
Subject: RE: [Xen-users] Xen-bridge throughput
From: Fasiha Ashraf <feehapk@xxxxxxxxxxx>
Date: Tue, 7 Jul 2009 12:30:45 +0530 (IST)
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Delivery-date: Tue, 07 Jul 2009 00:01:53 -0700
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veth1... veth3 are just 3 unused frontend network interfaces for Domain0.
They are created automatically when we setup xen-bridge.

Fasiha Ashraf

--- On Mon, 6/7/09, Fischer, Anna <anna.fischer@xxxxxx> wrote:

From: Fischer, Anna <anna.fischer@xxxxxx>
Subject: RE: [Xen-users] Xen-bridge throughput
To: "Fasiha Ashraf" <feehapk@xxxxxxxxxxx>
Date: Monday, 6 July, 2009, 1:51 PM

What are the vethX device in your setup? You are using VLANs? This might have some additional overhead, so you might want to try and disable those.


From: Fasiha Ashraf [mailto:feehapk@xxxxxxxxxxx]
Sent: 03 July 2009 08:18
To: Fischer, Anna
Subject: RE: [Xen-users] Xen-bridge throughput


Yeah... I am measuring CPU utilization with different ways. xm top, top and even i observed it using vmstat 1
to monitor it every sec while running netperf in guests. CPU parameter Idle just vary from 100% to 97%. That shows in communication only a little fraction of cpu is being utilized that is 1 to 3%.

PFA, the dom0 specs in detail.

Fasiha Ashraf

--- On Thu, 2/7/09, Fischer, Anna <anna.fischer@xxxxxx> wrote:

From: Fischer, Anna <anna.fischer@xxxxxx>
Subject: RE: [Xen-users] Xen-bridge throughput
To: "Fasiha Ashraf" <feehapk@xxxxxxxxxxx>
Date: Thursday, 2 July, 2009, 5:39 PM

Such a low CPU utilization is not normal. When I run netperf, the CPU is almost maxed out. Do you measure it using xm top?


Xen 3.0.3 is very old. You should consider upgrading to the latest Xen which is Xen 3.4!


Can you show what “brctl show” and “ifconfig” and “ifconfig –a” looks like on your system? It looks like you are not using a bridge but routing for your guests?


From: Fasiha Ashraf [mailto:feehapk@xxxxxxxxxxx]
Sent: 02 July 2009 12:36
To: Fischer, Anna
Subject: RE: [Xen-users] Xen-bridge throughput


Thanks alot for your concern. The guests were connected through a single bridge and bother are running PV in my case as well. I am Using Linux-2.6.18-6-xen-686 kernel. And the tool to measure throughput is same as yours(Netperf). I have told you that 8GB RAM (4 x 2 GB) is available in Dom0. While creating guest VMs I used this command to create a PV guest.

xen-create-image --hostname=D4G1 --size=7Gb --swap=1Gb \--ip= --netmask= --gateway= \--dir=/home/xen \--debootstrap --dist=etch --mirror=http://ftp.us.debian.org/debian/ --passwd


Below is some general information about created guest

General Information


Hostname : D4G1

Distribution : etch

Fileystem Type : ext3

Size Information


Image size : 7Gb

Swap size : 1Gb

Image type : sparse

Memory size : 500Mb

Kernel path : /boot/vmlinuz-2.6.18-6-xen-686

Initrd path : /boot/initrd.img-2.6.18-6-xen-686

See! I allocated memory once(statically) and VM uses only allocated amount 512RAM.. About CPU utilization, yes I have measured it while running netperf and observed it very low. Only 1% to 3% CPU was utilized during communication. Xen version is xen-hypervisor-3.0.3-1-i386.
I have flushed all type of packet filtering in Dom0 using this command iptables -F. There is some strange thing that I observed about it. When I check the TX and RX packets by xm top its about 5.6GB. But the netperf throughput results are 15.26Mbps.
I am running it for 300sec (5min), to get the stable results.
I am not getting whats wrong with it...

Fasiha Ashraf

--- On Wed, 1/7/09, Fischer, Anna <anna.fischer@xxxxxx> wrote:

From: Fischer, Anna <anna.fischer@xxxxxx>
Subject: RE: [Xen-users] Xen-bridge throughput
To: "Fasiha Ashraf" <feehapk@xxxxxxxxxxxx>
Cc: "xen-users@xxxxxxxxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxxxxxxxx>
Date: Wednesday, 1 July, 2009, 2:43 PM

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?

Fasiha Ashraf


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