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Re: [Xen-users] Gigabit Interface - XEN Full Virtualization

To: "Riccardo Veraldi" <Riccardo.Veraldi@xxxxxxxxxxxx>
Subject: Re: [Xen-users] Gigabit Interface - XEN Full Virtualization
From: "Emre Erenoglu" <erenoglu@xxxxxxxxx>
Date: Sun, 2 Dec 2007 20:07:41 +0100
Cc: Sadique Puthen <sputhenp@xxxxxxxxxx>, Artur Baruchi <mail.baruchi@xxxxxxxxx>, Mark Williamson <mark.williamson@xxxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
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Hi Riccardo, I tried to understand how you do it. I'm also trying to use my HVM domU with PV drivers. If I understand right, the important point is:

- use the source code of the XEN in the Dom0 (don't download from Xensource etc.). Is it true?

So, for example, if I'm using Fedora 8 as my Dom0, I have to download the source rpm of the xen-hypervisor that's running in Fedora 8. then go inside the unmodified_drivers and do the compilation. right?

I did like this for my system, unfortunately, either the system crashes completely or network stops working after some time... I guess there's a bug somewhere. For example, when unloading the xen-vnif module, I receive an error in dmesg talking about some "memory leak".



On Dec 2, 2007 5:08 PM, Riccardo Veraldi <Riccardo.Veraldi@xxxxxxxxxxxx> wrote:

if you compile the netfront drivers on your guest kernel and load them
as kernel module on your guests, you will have gigabit speed on a fully
virtual machine, hust use netfront and not ioemu then load
the kernel drivers on the virtual machine.
I have written something about it but it is in italian.
If you understand italian...


you should understand the way to do it even if it is written in italian.

I can translate in english if really it is needed


Artur Baruchi ha scritto:
> Hi Mark,
> Unfortunately, I did some tests, and even my nic being a giga and my
> lan supporting giga, my full virtualized domain wasnt able to pass
> 100Mb/sec. My paravirtualized guests had a very good performance in
> this environment.
> Thanks,
> Att.
> Artur Baruchi
> On Dec 2, 2007 12:34 AM, Mark Williamson < mark.williamson@xxxxxxxxxxxx> wrote:
>>>> I noted that the lspci output are different, and I would like to know,
>>>> how can I make my xen virtual machine see the same Hardware, so I can
>>>> force a 1000 Full speed.
>>> You can't get Gigabit speed for your NIC in HVM.  Whatever network cards
>>> you have on the physical system, it's emulated as a 10/100 mbps Realtek
>>> card to the HVM.
>>> Use paravirtualized drivers for HVMs to enhance the network card
>>> performance and throughput, but don't expect 1000 mbps.  :-)
>> The virtual machine won't have hardware matching the physical system; it just
>> sees whatever hardware Xen is emulating.
>> Xen doesn't emulate a GigE network card so you won't be able to see one in the
>> guest.  However, I suspect that the 10/100mbps card will be able to transmit
>> above that speed if your machine can emulate the card fast enough: because
>> there's not a real hardware 100mbps ethernet card there, there actually
>> shouldn't be anything limiting the speed to that.
>> As Sadique mentioned, if you use paravirtualised drivers in your guest (either
>> by using a PV guest or by installing paravirt network drivers in an HVM
>> guest) you could potentially increase the throughput and decrease the CPU
>> overhead further.
>> Cheers,
>> Mark
>> --
>> Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
>> Mark: To answer a question with a question: What use is a skateboard?
>> Dave: Skateboards have wheels.
>> Mark: My wheel has a wheel!
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