Re: domU network slowdown with new dom0 kernel

[Jeremy Fitzhardinge <jeremy@goop.org>]

On 03/01/2010 04:57 AM, Denis Chapligin wrote:
> Hi
>
> I have a domU that acts as iSCSI target for our network. It was running
> on the host with xen 3.4.2 and original XenLinux (2.6.18) kernel. Today
> i've tried to replace old 2.6.18 kernel with a latest (stable/master)
> pvops kernel. The problem, is that when i replaced dom0 kernel, network
> performance of domU mentioned above dropped and networking with this
> domU become totaly unusable. In domU's dmesg i see the following
> entries:
>
> [ 1785.260012] net eth0: rx->offset: 0, size: 4294967295
> [ 1785.260036] net eth0: rx->offset: 0, size: 4294967295
> [ 1785.810612] net eth0: rx->offset: 0, size: 4294967295
> [ 1785.810612] net eth0: rx->offset: 0, size: 4294967295
> [ 1786.310061] net eth0: rx->offset: 0, size: 4294967295
> [ 1786.310081] net eth0: rx->offset: 0, size: 4294967295
> [ 1786.550007] net eth0: rx->offset: 0, size: 4294967295
> [ 1786.550024] net eth0: rx->offset: 0, size: 4294967295
> [ 1786.970010] net eth0: rx->offset: 0, size: 4294967295
> [ 1786.970025] net eth0: rx->offset: 0, size: 4294967295
> [ 1792.840010] __ratelimit: 6 callbacks suppressed
> [ 1792.840035] net eth0: rx->offset: 0, size: 4294967295
> [ 1792.840049] net eth0: rx->offset: 0, size: 4294967295
> [ 1798.310016] net eth0: rx->offset: 0, size: 4294967295
> [ 1798.310045] net eth0: rx->offset: 0, size: 4294967295
> [ 1799.230013] net eth0: rx->offset: 0, size: 4294967295
> [ 1799.230036] net eth0: rx->offset: 0, size: 4294967295
> [ 1799.550009] net eth0: rx->offset: 0, size: 4294967295
> [ 1799.550031] net eth0: rx->offset: 0, size: 4294967295
> [ 1800.110352] net eth0: rx->offset: 0, size: 4294967295
> [ 1800.110352] net eth0: rx->offset: 0, size: 4294967295
> [ 1800.350020] net eth0: rx->offset: 0, size: 4294967295
> [ 1800.350050] net eth0: rx->offset: 0, size: 4294967295
>
> in dom0's dmesg i see nothing interesting. I've tried several kernels
> and found that domU could use any kernel, but dom0 kernel version is
> critical and it only works with xen 2.6.18 kernel.
>
> I have 6 xen hosts, but only this domU is problematic. The domU above is
> very high loaded and installed on host with 4x1GB ethernet card,
> combined into single etherchannel. All other domU's on other hosts
> and this host aren't affected and use only 1 NIC and they're
> bandwidth usage usually not more than 10-15% of that NIC. The
> problematic domU uses up to 80% of combined bandwidth.
>
> So, what i'm doing wrong and how can i fix this issue? :)
>
>    

Is this with a freshly checked out version of xen.git?  I committed some 
bugfixes to netback last week, which may have caused problems.

     J