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

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Monday, November 12, 2012, 5:32:04 PM, you wrote:

> On Mon, Nov 12, 2012 at 03:50:24PM +0100, Sander Eikelenboom wrote:
>> 
>> 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.

> Were you ever able to trigger the BUG_ON in the patch that Ian posted?

What exact patch (or any other patch that can help you ) ?
(so i can try again to be sure)


>> I haven't seen issues with netfront and netback before this commit. FWIW: 
>> the hardware nics in this machine are two r8169 's.
>> 
>> --
>> Sander
>> 
>> > 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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