Xen users - Mar 2008 - poor network performance on domU

Hi all,

I recently started with Xen (3.1.0) on my new server running Ubuntu  
Gutsy (7.10) and I''m experiencing very poor network performance on my  
domU''s.

Since my colo provider offers me a /28 of routed public IPs next to  
one interconnection IP to their routers, I built a Xen configuration  
as described in http://www.debian-administration.org/articles/360 (a  
routed setup instead of the default bridged). This works as expected:  
all domU''s are accessible from the internet.

The network performance of the Dom0 is fine: I can saturate my 100Mb/ 
sec uplink both by uploading and downloading. Performance towards the  
domU is fine as well. Performance from the DomU''s to the internet  
however is dramatic: speeds start at 2-3MB/sec but quickly drop to  
just a few KB/sec (!). Transfer of large files never end at all.

The server I''m running this on is a Supermicro H8SSL-i2 with and AMD  
Opteron 1218 Dual Core proc, 4GB RAM, the NIC is a Broadcom 1G  
interface connected to a 100Mb/sec switchport at my ISP.

I''ve tried searching these archives (and the internet) for any clue  
what might cause this poor upload performance, but failed to find  
anything really useful.

If anyone has hints and tips on how to make my DomU''s uplink speed  
normal, I''d really appreciate it. I really have no idea where to look  
now :(

TIA,

Teun



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On Saturday 22 March 2008 13:07:35 Teun Vink wrote:
> The network performance of the Dom0 is fine: I can saturate my 100Mb/
> sec uplink both by uploading and downloading. Performance towards the
> domU is fine as well. Performance from the DomU''s to the internet
> however is dramatic: speeds start at 2-3MB/sec but quickly drop to
> just a few KB/sec (!). Transfer of large files never end at all.
how is your domU to other domU speed?
if it is even worse then the problems you describe are similar to mine i had 
after updating to xen3.
Then a helpfull soul on IRC gave me the hint to do
"ethtool -K eth0 tx off"  in the domUs. that helped dramaticly. looks
like a
bug in xen.


-- 
best regards/Mit freundlichen Grüßen
Arvid Ephraim Picciani

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On Mar 22, 2008, at 1:11 PM, Arvid Ephraim Picciani
wrote:
> On Saturday 22 March 2008 13:07:35 Teun Vink wrote:
>> The network performance of the Dom0 is fine: I can saturate my 100Mb/
>> sec uplink both by uploading and downloading. Performance towards the
>> domU is fine as well. Performance from the DomU''s to the
internet
>> however is dramatic: speeds start at 2-3MB/sec but quickly drop to
>> just a few KB/sec (!). Transfer of large files never end at all.
> how is your domU to other domU speed?
> if it is even worse then the problems you describe are similar to  
> mine i had
> after updating to xen3.
> Then a helpfull soul on IRC gave me the hint to do
> "ethtool -K eth0 tx off"  in the domUs. that helped dramaticly.  
> looks like a
> bug in xen.

Speed between domU''s was just as bad. I just applied your suggestion,  
and it''s given an enormous increase in speed: between domU''s I
get
around 20MB/sec, speed to the internet is limited by my uplink port now.

So thanks a lot for this hint!

Teun

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Am 22.03.2008 um 13:11 schrieb Arvid Ephraim Picciani:
> On Saturday 22 March 2008 13:07:35 Teun Vink wrote:
>>  Performance towards the
>> domU is fine as well. Performance from the DomU''s to the
internet
>> however is dramatic: speeds start at 2-3MB/sec but quickly drop to
>> just a few KB/sec (!). Transfer of large files never end at all.
> Then a helpfull soul on IRC gave me the hint to do
> "ethtool -K eth0 tx off"  in the domUs. that helped dramaticly.
For me you are this helpful soul. I had this problem for half a
year now and no idea how to fix it. Network performance from a
domU to external systems as been as low as 4-8kBytes/sec. Now this
is fixed.

Thank you very much.
> looks like a bug in xen.
Is this a known bug for Xen developers and are there any plans to
fix this?

Regards
Ralf

-- 
Van Roy''s Law: -------------------------------------------------------
        An unbreakable toy is useful for breaking other toys.



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Is this something that has to be done each time the domU is rebooted?

Ralf Müller wrote:
>
> Am 22.03.2008 um 13:11 schrieb Arvid Ephraim Picciani:
>> On Saturday 22 March 2008 13:07:35 Teun Vink wrote:
>>>  Performance towards the
>>> domU is fine as well. Performance from the DomU''s to the
internet
>>> however is dramatic: speeds start at 2-3MB/sec but quickly drop to
>>> just a few KB/sec (!). Transfer of large files never end at all.
>> Then a helpfull soul on IRC gave me the hint to do
>> "ethtool -K eth0 tx off"  in the domUs. that helped
dramaticly.
>
> For me you are this helpful soul. I had this problem for half a
> year now and no idea how to fix it. Network performance from a
> domU to external systems as been as low as 4-8kBytes/sec. Now this
> is fixed.
>
> Thank you very much.
>
>> looks like a bug in xen.
>
> Is this a known bug for Xen developers and are there any plans to
> fix this?
>
> Regards
> Ralf
>
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Am 24.03.2008 um 16:13 schrieb James Wilson:
>>> Am 22.03.2008 um 13:11 schrieb Arvid Ephraim Picciani:
>>> Then a helpfull soul on IRC gave me the hint to do
>>> "ethtool -K eth0 tx off"  in the domUs. that helped
dramaticly.
> Is this something that has to be done each time the domU is rebooted?
I would say yes. I added it to /etc/init.d/boot.local in all my domU''s.

Ralf

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