TCP CUBIC and IPoIB

I wonder if anyone has ever looked at this? It looks like there is something wrong here.

I was just looking at some results from a stock 2.6.35 kernel doing TCP over IPoIB (2k MTU) and CUBIC looks like it is going nutz, you can see in a bandwidth plot a fairly characteristic saw tooth pattern, and diminished bandwidth. The effect compounds rather dramatically as the RTT goes up.

This isn't really my area of expertise, so I wonder if someone else has looked into this? Errant congestion events will sap bandwidth even on low latency links..

Cheers,
Jason
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