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

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Subject: Re: [Xen-users] Gigabit Interface - XEN Full Virtualization
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Sun, 2 Dec 2007 02:34:43 +0000
Cc: Sadique Puthen <sputhenp@xxxxxxxxxx>, Artur Baruchi <mail.baruchi@xxxxxxxxx>
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> > 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.


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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