[ofa-general] Re: [Bug 458] Heavy interrupt rates kill UDP performance

[Michael S. Tsirkin]

> I can reproduce this with OFED 1.2rc1 IPoIB UD, dual Xeon 5160 (in Dell
> PE1950), and Cheetah DDR HCA:

This looks exactly like receive side live lock - unfortunately since
it was decided not to include NAPI in OFED 1.2, there's not
much can be done here. And I expect you'll see the same behaviour
with OFED 1.1.

You can try increasing the ipoib recv_queue_size by using the appropriate
module parameter. Of course, bigger recv_queue_size results in worse
CPU cache utilization pattern, so performance might suffer for other
workloads.

> The problem is NOT there in IPoIB CM:

Probably because IPoIB CM uses 64KB messages, so the interrupt rate is
reduced by a factor of 32.

-- 
MST