Re: [Xen-devel] large packet support in netfront driver and guest network throughput

[Anirban Chakraborty <abchak@xxxxxxxxxxx>]

On Sep 19, 2013, at 2:41 AM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:

> On Wed, Sep 18, 2013 at 08:38:01PM +0000, Anirban Chakraborty wrote:
>> 
>> On Sep 18, 2013, at 8:48 AM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
>> 
>>> On Tue, Sep 17, 2013 at 05:53:43PM +0000, Anirban Chakraborty wrote:
>>>> 
>>>> 
>>>> On 9/17/13 1:25 AM, "Wei Liu" <wei.liu2@xxxxxxxxxx> wrote:
>>>> <snip>
>> 
>> Yes, it is 2.6.32-358.el6.x86_64. Sorry, I missed it out last time.
>> 
> 
> So that's a RHEL kernel, you might also want to ask Redhat to have a
> look at that?

It is not RHEL kernel, Centos 6.4. This being a netfront driver issue, I think 
we should address it here.

> 
>>> <snip>-- 
>>> 1.7.10.4
>> 
>> 
>> I was able to see a bit of improvement (from 2.65 to 3.6 Gbps) with the 
>> following patch (your patch plus the advertisement of NETIF_F_GRO) :
> 
> OK, thanks for reporting back.
> 
> I'm curious about the packet size after enabling GRO. I can get 5G/s
> upstream with packet size ~24K on a 10G nic. It's not line rate yet,
> certainly there is space for improvement.

I am seeing varying packet sizes with the GRO patch, from 2K to all the way 
upto 64K.
I do not think we can get line rate by enabling GRO only. The netback thread 
that is handling the guest traffic is running on a different CPU (and possibly 
different node) compared to the guest. If we can schedule netback for a guest 
to run on the same node as the guest, we should be able to see better numbers. 
In any case, are you going to submit the patch upstream or should I do it? 
Thanks.

Anirban




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