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Re: [Xen-devel] xen.git branch reorg
 
- To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>,	Christophe Saout <christophe@xxxxxxxx>
 
- From: Boris Derzhavets <bderzhavets@xxxxxxxxx>
 
- Date: Sat, 25 Apr 2009 02:22:20 -0700 (PDT)
 
- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>,	Ian Campbell <Ian.Campbell@xxxxxxxxxx>
 
- Delivery-date: Sat, 25 Apr 2009 02:22:50 -0700
 
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- List-id: Xen developer discussion <xen-devel.lists.xensource.com>
 
 
 
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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