[Xen-users] Re: TX Checksum

[Stephen Bosch <posting@xxxxxxxxxxx>]

Jim Henderson wrote:
> Hello,
> 
> In xen 3.0.1 kernel 2.6.12.6, I can do the following in a DomU:
> 
> # ethtool -K eth0 tx off
> 
> http://wiki.xensource.com/xenwiki/XenFaq says this will fix TCP and UDP
> checksum errors, as well as other networking problems as many posts have
> claimed.  I do this because it somehow makes bridging work properly when
> I'm using a bonding interface on the bridge.
> 
> Question 1: Why can I not do this in a DomU in xen 2.0.7, kernel 2.6.11.12?
> 
> # ethtool -K eth0 tx off
> Cannot set device tx csum settings: Operation not supported
> 
> I seem to have similar problems in Xen 2, and that is why I am asking.
> For example, I will get network hangs in my domU's under certain high
> load conditions.
> 
> Question 2: Since I cannot seem to the tx checksumming value, what is
> the default for tx checksumming in xen 2.0.7?  If it's "ON", how would I
> turn it "OFF"?
> 
> (So why do I not just use Xen 3?  Well, I'm not ready to put Xen 3.0
> into production.  The occasional "zombie domains" I'm seeing in a
> testing environment do not inspire confidence.  Zombies also make the
> test system hang when rebooting, because "xm shutdown --all --wait
> --halt" will hang.)

It's funny -- we're having all these problems too. I posted some time
back about a Bacula problem that we suspect is being caused by this
transmit checksum issue, but didn't get any response -- at least, not
from the developers. (To the folks who with Dell machines who responded,
many thanks -- so far, we've tried all the offered fixes, and it doesn't
look like a Dell problem, so we're back to seeing if we can fix Xen
ourselves).

I'm sorry I can't offer more help than that. We're as puzzled as you are.

I guess if Xensource hopes to charge money for the optimizer, there's a
lot of work to be done. We thought Xen was production ready, but maybe
that assessment was premature.

-Stephen-


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