Re: [Xen-users] HVM performance issues

[Ray Barnes <tical.net@xxxxxxxxx>]

Thanks for the reply.  I did find large sending offloads configured in
the domU (under Device Manager).  Based on something else I googled, I
turned them off and was able to resolve this fully.  My theory is that
those offloads were latent, which would explain why something with
microseconds of latency on my LAN would transfer quickly, but a couple
of msec further over the wire would not.  Thanks again.

-Ray


On Fri, May 4, 2012 at 4:12 AM, John Weekes
<lists.xen@xxxxxxxxxxxxxxxxxx> wrote:
> On 5/3/2012 6:26 PM, Ray Barnes wrote:
>>
>> Thanks for the replies.  I found and installed James' PV drivers,
>> version 0.11.0.357.  It did wonders for my disk throughput.  But it
>> also created a new problem with transmission throughput on the NIC.
>> Prior to the PV installation, I had a minimum of 50 megabits
>> bi-directional throughput, with the dom0 uplinked to the network via
>> FastE.  Now, post-installation, although my download throughput is
>> much faster and more consistent, my upload throughput out to the
>> Internet is extremely slow, on the order of 5 megabits/sec for a
>> single thread.  I can not duplicate this locally to my LAN - I'm able
>> to push 80 to 90 mbits/sec to the local LAN.  But every single test
>> I'm running to speedtest.net results in uploads between 1-5 mbits/sec.
>>  For reference, I'm able to do 50+ mbits/sec upload to the same
>> targets via a nonvirtualized Windows box on my network.  The problem
>> is definitely confined to the Windows domU (version 2003 R2).
>>
>> I'm invoking the vif like this:
>>
>> vif = [ 'type=iommu, mac=00:16:3e:00:00:09, bridge=something,
>> script=vif-something']
>>
>> I've also tried it with 'model=intel' appended but with no change.
>> Also, against my better judgment, I implemented the registry changes
>> mentioned at
>> http://msdn.microsoft.com/en-us/library/ee377084%28v=bts.10%29.aspx
>> for better network performance (via the supplied PowerShell script at
>> the bottom), no change also.
>>
>> Any idea what's happening?
>
>
> I've seen problems with GSO and TSO causing corrupted checksums for packets
> with certain properties in the past, which might be affecting you here (this
> issue, if seen, would cause random dropped packets, killing transfer
> speeds). Try turning off TSO/GSO/GRO/LRO both in dom0 (using ethool -K) and
> on the virtual network adapter in the domU.
>
> Since you have the GPLPV drivers installed, you can also remove "type=iommu,
> " from the vif line. I don't know if it hurts to have it there, but it
> shouldn't hurt to remove it.
>
> -John

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