Improving the performance of my Xen VM

posted in Hypervisor
Tuesday, May 13 2014, 11:27 AM
Stefan
Stefan
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I am working for a company to get their operating system optimised in a virtual environment. It's a Unix derivative, capable of real-time computing. I've tested the performance of several devices independently to conclude that the overall performance is lacking. VGA performance is irrelevant but disk performance and network performance are crucial and still inefficient.

Ultimately our goul is to get a virtual machine to be capable of handling big loads of network traffic. I've read an interesting article stating that Xen isn't good at networking compared to other VMM's. However this article is outdated (about Xen 3.0). I wonder where I need to dig. I am sure others have already encountered and/or solved this problem.

I also read about RT-Xen, anybody has some experience with it here?

Please share your ideas, experiences and solutions with me! Thanks.

Example of my "working" config:
builder='hvm'
vcpus='1'
memory='256'
disk=['/usr/img/gp.raw,,hda,w']
name='VrooM'
vif=['mac=00:16:3e:01:01:01, bridge=xenbr0, model=pcnet']
on_poweroff='destroy'
on_reboot='destroy'
on_crash='destroy'
boot='dc'
acpi='1'
apic='1'
viridian='1'
xen_platform_pci='1'
sdl='0'
vnc='1'
vnclisten='0.0.0.0'
vga="cirrus"
usb='1'
usbdevice='tablet'
serial='pty'
device_model_version="qemu-xen"
device_model_override="/usr/bin/qemu"

Accepted Answer

Tuesday, May 13 2014, 05:45 PM - #permalink
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Stefan,

For experiences surrounding XenRT, you'll probably find more experience over in the xen-users mailing list. This Q&A area is more for basic answers. You'll even find more performance people in xen-users, but let's see if we can't get you started in the right direction.

There are general performance considerations which can be valuable. Check out this document:

http://wiki.xenproject.org/wiki/Tuning_Xen_for_Performance

And have you seen this networking performance guide?

http://wiki.xenproject.org/wiki/Network_Throughput_and_Performance_Guide

It received its last serious update about 2 years ago, and it is focused on XenServer/XCP, but I believe it should contain some useful information.

It appears you are using PV drivers on HVM, which should have better performance than straight HVM (you can see some moderately recent benchmarks for HVM vs PVHVM here: https://xen-orchestra.com/debian-pvhvm-vs-pv/ ). Also, PVHVM is likely newer technology (with better performance) than what was descibed in the old paper you mentioned. Straight HVM was often criticized for weak performance, which is why modern Xen Project installations focus on PVHVM and the recently released PVH (which is designed to be the most performant mode once code optimizations are completed in the next release or so).

More performance docs can be found here:

http://wiki.xenproject.org/wiki/Category:Performance

Does this help at all?

Russ
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  • Accepted Answer

    Stefan
    Stefan
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    Thursday, May 15 2014, 12:01 PM - #permalink
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    Thank you for your quick and detailed response Russell, most appreciated.
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