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[Xen-users] Very bad network performance between domU and dom0

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Subject: [Xen-users] Very bad network performance between domU and dom0
From: Klaus Schmidinger <Klaus.Schmidinger@xxxxxxxxxx>
Date: Thu, 25 Jan 2007 14:18:34 +0100
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I have a PC with an Intel Core 2 Duo E6600 2,40GHz F1066 CPU
that runs openSUSE 10.2. The VT feature in the BIOS is enabled.
The XEN version is 3.0.3_11774.

uname -a:
Linux tiger #1 SMP Mon Nov 27 11:46:27 UTC 2006 x86_64 x86_64 
x86_64 GNU/Linux

I have two virtual mahines, one running SUSE 8.2, the other Windows XP.
The Linux machine mounts the /home directory from an external server
via NFS, and the Windows machine does the same via Samba. In both cases
access to the files on the external server is very slow.

My measurements showed that the data transfer rate between the
external server and my PC that runs the dom0 is about 90MB/s over
a gigabit ethernet connection, which is perfectly ok.

The same measurements between the dom0 and the Linux domU machine show

dom0 -> domU   27.7 MB/s
domU -> dom0    7.9 MB/s

which is very bad considering that this is all within the same
hardware and nothing has to go over any external network connection.

ifconfig doesn't report any network errors on any of the interfaces.

I searched the archive of this ML and came across several threads
with similar problems, but couldn't find any real solution.

This is a real showstopper for me, because if I can't have good
access to the NFS/Samba mounted home directory, there's no point in
using virtual machines at all. So any hints that could help to
improve this are greatly appreciated.


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