Re: [Qemu-devel] idea: non-ethernet paravirtual network device

[Sassan Panahinejad <sassan@sassan.me.uk>]

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Ok, thanks guys. I don't think I'll proceed with this idea.

Thanks
Sassan

On 26 July 2011 11:23, Hannes Reinecke <hare@suse.de> wrote:

> On 07/26/2011 08:04 AM, Stefan Hajnoczi wrote:
>
>> On Mon, Jul 25, 2011 at 4:53 PM, Sassan Panahinejad<sassan@sassan.me.**uk<sassan@sassan.me.uk>>
>>  wrote:
>>
>>> Here's a thought, could we improve network performance by creating a
>>> paravirtual network device which doesn't emulate ethernet? It shouldn't
>>> be
>>> too hard to just whack IP packets pretty much directly over a virtio
>>> link.
>>> This should improve performance when using a "user" host connection and
>>> we
>>> could introduce a tun host connection instead of tap for this setup.
>>>
>>> Does anyone have any thoughts on how worthwhile this would be? Would the
>>> performance improvement justify the effort involved?
>>>
>>
>> My guess is no noticable impact (if you ignore ARP requests).
>>
>> The Ethernet header is only 14 bytes or so.  We don't calculate any
>> checksums at that level.  There's probably not much of a win.
>>
>>  Only lots of pain to be had.
> Mainframe used to do this. But abandoned it not, thankfully.
>
> Problem is that you need to patch each and every tool looking at the
> packets to _not_ expecting an Ethernet header.
> And patching up DHCP is _not_ trivial.
>
> Cheers,
>
> Hannes
> --
> Dr. Hannes Reinecke                   zSeries & Storage
> hare@suse.de                          +49 911 74053 688
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
> GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
>
>

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