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xen-devel
Re: [Xen-devel] xen.git branch reorg
I've just tested:-
# /usr/local/sbin/ethtool -K eth0 tso off
at Ubuntu 9.04 Server PV DomU at Xen 3.4-rc3-pre Dom0 ( with 2.6.30-rc3-tip).
This command also fixes remote VNC connections performance to DomU.
Boris.
--- On Fri, 4/24/09, Christophe Saout <christophe@xxxxxxxx> wrote:
From: Christophe Saout <christophe@xxxxxxxx>
Subject: Re: [Xen-devel] xen.git branch reorg
To: "Jeremy Fitzhardinge" <jeremy@xxxxxxxx>
Cc: bderzhavets@xxxxxxxxx, "Xen-devel" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Ian Campbell" <Ian.Campbell@xxxxxxxxxx>
Date: Friday, April 24, 2009, 6:39 PM
Hi Jeremy,
> > In meantime time i see, that 2.6.30-rc3&rc2&rc1-tip
are
affected.
> > Solution is the same as on Solaris xVM Linux DomUs about one
> > year ago - is to disable checksum (nothing else) offloading at
Linux
> > DomUs ( CentOS 5.3, Ubuntu 9.04)
> >
> > /usr/local/sbin/ethtool -K etho tx off
>
> OK, that's a good lead.
Yes, I've been seeing this too (and meant to investigate it before
claiming there's abug) and I can confirm that turning off segmentation
offloading "cures" the problem here too.
Now the tcpdump on Dom0 looks interesting. It repeatedly sees a packet
with 2880 byte from DomU coming in, which is then dropped and ICMP
"fragmentation needed" sent back, the DomU resends a 1440 byte packet
(after some delay), which then goes through, but then the next one is a
2880 byte one again, and so on.
FYI: My Dom0 is running NAT, in case this is relevant.
Christophe
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