Re: help with horrible network failures

[Nivedita Singhvi <niv@us.ibm.com>]

Ian Pratt wrote:

>>I've got two machines running identical versions of xen & 
>>linux. One of 
>>them constantly has problems under high network loads 
>>(70-100% httperf 
>>loads). This is using xen-unstable checked out on or about 
>>Feb 13. Any 
>>clues? See below for details.
> 
> 
> One machine exhibits the bug, the other doesn't? How similar is the h/w?

I believe this is a known unresolved bug in mainline.
It's possible Rob is provoking it by using NAPI - and
it is load-related, so that might explain why one box
is seeing it and one isn't. Essentially, data is getting
reordered where it really shouldn't, due to a race that
isn't clear. It would be very helpful to track this down
finally - if it hasn't already..

> Can you reproduce with a single high-rate TCP stream? Do you have any of
> the iptables/netfilter connection tracking stuff in your kernel?

> Can you reproduce with an older version of Xen?

I suspect that it is independent of Xen - unless some versions
of Xen slow down traffic enough to change the window..

thanks,
Nivedita


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