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

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Klaus Schmidinger
> Sent: 25 January 2007 14:45
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] Very bad network performance between 
> domU and dom0
> 
> Petersson, Mats wrote:
> >  
> > 
> >> -----Original Message-----
> >> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> >> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> >> Klaus Schmidinger
> >> Sent: 25 January 2007 13:19
> >> To: xen-users@xxxxxxxxxxxxxxxxxxx
> >> Subject: [Xen-users] Very bad network performance between 
> >> domU and dom0
> >>
> >> 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 2.6.18.2-34-xen #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
> > 
> > I take it this is a HVM domain and not a para-virtual kernel?
> 
> Yes - otherwise I believe wouldn't be able to run Windows XP 
> as a guest.

Yes, but you were also talking of Linux guests, which CAN be either - so
I just wanted to make sure that we're talking about the same thing. 
> 
> >> 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.
> > 
> > How have you configured your DomU/Dom0 cpu partitioning? Having one
> 
> I didn't do anything special about this, so it should be at the
> default settings.

Which means "everything on all CPU's". 
> 
> > dedicated CPU running Dom0 and another running DomU will 
> help a little
> > bit because the context switching between the two is a 
> little bit better
> > - how much better is a question for debate. 
> > 
> > Bear in mind tho', that the main culprit here is the fact 
> that you're
> > using a emulated network card. It's unlikely that you'll 
> ever get HIGH
> > performance with this, because it's just too software 
> intensive (several
> > thousand cycles for each intercept by Xen of any operation 
> that goes to
> > the hardware). 
> > 
> > The best solution is to use the para-virtual drivers - 
> these should (in
> > theory at least) give you about the same performance as the 
> para-virtual
> > kernel does on Xen, because it's using the same method. 
> > 
> > For linux-2.6, those are available in <xen source
> > directory>/unmodified_drivers. The README file in that 
> directoy tells
> > you how to build these drivers. It's easiest if you do this ON the
> > target-system. 
> > 
> > There are drivers for Windows as well, but those are not 
> available in
> > source-form, but I believe XenExpress contains drivers for 
> Windows if
> > you want to get those. 
> 
> I just took a look at the XenEnterprise-3.1.0-install.iso and there
> is a xenserver-client.exe and a xe.exe. I would like to just replace
> the network driver as necessary, without having to fully install the
> whole xen thing on my virtual Windows XP machine. Can you give me any
> hints on how to do this?

I don't know how you actually install it, but in effect, you'd be
installing a driver inside your Windows in one way or another. I don't
think XenServer-client.exe is the right file, but I don't KNOW what the
file is, so I'm just guessing here - I haven't actually ever used PV
drivers on any of my virtual machines. 

--
Mats
> 
> Klaus
> 
> > Mats
> >> Klaus
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
> 
> 
> 



_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users