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

Monday, November 12, 2012, 3:28:35 PM, you wrote:

> 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.

After the issues with netback where fixed, I'm seeing the issues with net_front 
reverting the single commit 5640f7685831e088fe6c2e1f863a6805962f8e81 (that was 
pointed out for netback) also makes these disappear.
I haven't seen issues with netfront and netback before this commit. FWIW: the 
hardware nics in this machine are two r8169 's.


> 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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