RE: [Xen-users] More Windows network performace issues.

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> 
> Made considerable progress with networking problems.
> New anti-virus and new gplpv driver helped a lot.
> 
> I'm still having poor speed to the external network.
> 
> Dom0 is debian squeeze using the debian dom0 kernel. Xen is 4.0.1 from
source.
> 
> Tested domu windows in server 2008 with new gplpv drivers.
> Reference debian pv domu is debian squeeze.
> All are 64 bit.
> External site is a xen dom0 as it's the fastest available.
> All tests with iperf in Mbits/sec
> Did each a few times and they were pretty consistent.
> I put down the highest number.
> 
> domu server 2008 > dom0   618
> domu server 2008 > external 280
> domu server 2008 > domu squeeze  533
> domu squeeze > dom0   4000
> domu squeeze > external  923
> dom0 > external   933
> 
> The one that concerns me is:
> domu server 2008 > external 280
> 
> Need to access external file shares and that is quite a hit.
> Why does a hvm domain take an additional hit in the bridging to the
external
> interface?
> 
> Any ideas?
> 

I'm getting similar results. About 1GBits/second to Dom0 and
200MBits/second to an external host (over gigabit).

I just tested an XP machine and got the following with -w1m -l32k
options to iperf:
(Ext is just a gigabit LAN to another Xen physical machine)

DomU -> Dom0 - 5Gbits/second
Dom0 -> DomU - 800Mbits/second
Dom0 -> Ext  - 940Mbits/second
Ext  -> dom0 - 950Mbits/second
DomU -> Ext  - 930Mbits/second
Ext  -> DomU - 950Mbits/second

So it does seem to be 2008 specific.

The problem you are seeing may be something to do with the fact that
under Vista and above, Windows has to use a compatibility layer to make
my NDIS5.1 driver work at all. The fact that a driver written for an 8
year old OS works at all says something about Microsoft's commitment to
backwards compatibility, but there are definitely some performance costs
associated with it. I don't understand why it would be slower to an
external host though.

One of these days I'll port xennet to NDIS 6.x and I hope to see some
fairly impressive performance increases, but I just don't have the time
right now, plus it means maintaining two versions of xennet etc.

James


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