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Re: [Xen-devel] domU to domU networking issues in v3.7? (netserver/netperf failing to communicate)

On Mon, Nov 12, 2012 at 09:54:44AM +0000, Ian Campbell wrote:
> On Sat, 2012-11-10 at 13:59 +0000, Konrad Rzeszutek Wilk wrote:
> > Hey Ian, Xen-devel mailingl list,
> > 
> > I think the issue of 70% traffic lost was actually introduced in v3.6 or
> > perhaps v3.5. Annie and Marcos (CC-ed here) are looking to see which of
> > the releases introduced this. The issue we are seeing is that a domU
> > to domU communication breaks - this is with netperf/netserver talking to
> > each other.
> > 
> > Anyhow, I think the 3.7 compound page exacerbated the problem and also
> > (at least on some of my test hardware) exposed existing issues with
> > drivers. The issue I have is that the 'skge' driver has a bug that has
> > been there for ages (I tested way back to 3.0 and still saw it) were it
> > can not work with SWIOTLB. It is probably missing an pci_dma_sync
> > somewhere. 
> > 
> > Anyhow the compound page got me to look at Xen-SWIOTLB and that looks
> > OK. Even with synthetic driver (the fake one I posted somewhere) it
> > dealt with compound pages properly (with debug or non-debug Xen
> > hypervisor).
> The debug build is probably most interesting since it deliberately
> allocates a non 1-1 p-to-m mapping so as to catch exactly these sorts of
> issues.

Right. My test env runs with that. And so far it only has issues
with the skge one.
> > So was wondering if you had looked at this in more details? Any
> > ideas? Or would it be more prudent to ask that once we know for sure
> > which Linux release introduced the communication failures between
> > guests?
> I've not looked at it any further I'm afraid.
> If these changes (be they in 3.5 or later, or earlier) are exposing
> driver bugs then I suspect the netdev chaps would want to know about it.

Right. Annie (CC-ed here) mentioned to me that v3.5 looks to work ok.
And is off checking v3.6. v3.7 is definitly a no go.
> FWIW I see the issue with tg3.

I should double-check that but I didn't get any issues with the tg3 I had.

I was running the netperf/netserver from/to to see if I could reproduce the
issues (70% loss) you described but did not have much luck.

> Ian.

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