Re: Xen emulated network cards (was Re: FreeBSD HVM guests?)

[Thor Lancelot Simon <tls%rek.tjls.com@localhost>]

On Wed, May 20, 2009 at 07:58:10PM +0100, Stephen Borrill wrote:
>
> The qemu 0.9.1 man page says:
> Qemu can emulate several different models of network card.  Valid values 
> for type are "i82551", "i82557b", "i82559er", "ne2k_pci", "ne2k_isa", 
> "pcnet", "rtl8139", "smc91c111", "lance" and "mcf_fec".
>
> I guess any of these are potential alternatives to e1000 on xen 3.1.4, 
> but are any of them any better than ne2k_pci?

Any of 82551, 82557, or 82559 should work with the 'fxp' driver.  They
have a reasonable DMA interface (ne2k_pci is so slow because it uses PIO,
which must be emulated on a word-by-word basis!) and should be acceptably
fast.

"pcnet" should work with our "pcn" or "le" drivers and "lance" should
work with our "le" driver.  I have noticed some problems with emulated
pcnet devices in the past, though.  The main advantage to using pcn
instead of le is a larger dma descriptor ring.

A few of these devices may support interrupt mitigation, which would
further reduce emulation overhead, but I fear none of our drivers do.
That, plus TSO, would be the big win to using an emulated e1000.

-- 
Thor Lancelot Simon                                        
tls%rek.tjls.com@localhost
    "Even experienced UNIX users occasionally enter rm *.* at the UNIX
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