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Re: [Xen-users] Xen Performance

To: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Subject: Re: [Xen-users] Xen Performance
From: Grant McWilliams <grantmasterflash@xxxxxxxxx>
Date: Fri, 16 Oct 2009 07:43:31 -0700
Cc: Dustin.Henning@xxxxxxxxxxx, xen-users@xxxxxxxxxxxxxxxxxxx
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On Fri, Oct 16, 2009 at 6:07 AM, Fajar A. Nugraha <fajar@xxxxxxxxx> wrote:

> 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.


Agreed on the bridge setup. You do get the best speed out of it. Also as I'm slowly seeing that if you throw more hardware at the solution the
inefficient path of Dom0 to DomU does get faster. On my Dual Core Duo Xeon that speed is 400Mb/sec but on the newer Core2 Duo based Xeon I'm getting about double that. The ratio seems to be the same on DomU - DomU, Domu - Dom0 and Dom0 - DomU telling me that it's a xen architecture issue. Getting close to wire speed at my slowest link is nice but I'd sure like to see those 2-3 Gb numbers everywhere. :-)

I have so many other areas I need to tune that this issue for now is a non-event. I just read yesterday that Redhat is swearing that you can run more KVM VMs on a piece of hardware than you can Xen VMs. I currently have 41 VMs on one 8 core Xeon for a classroom environment (nxclient) and it's dogging but I have a lot of things I can do to help pick up the pace.

Thanks for the input everyone.

Grant McWilliams

Some people, when confronted with a problem, think "I know, I'll use Windows."
Now they have two problems.

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