[ofa-general] Re: [PATCH 1/5] IB/ipoib: Split CQs for IPOIB UD

[Eli Cohen]

On Fri, 2008-02-01 at 01:45 -0800, Shirley Ma wrote:
> I filed a patch back two years ago to split CQ. The feedback was it
> didn't benefit mthca since it had only one interrupt shared between send
> and recv. More context switches were generated when splitting CQ. Then I
> decided to wait the multiple interrupt vector to be implemented in
> device driver layer to push this patch later with multiple interrupt
> vectors (This is the next item on my list). The why the performance got
> improved without multiple interrupt support here?
> 

In my approach, I use two CQs but the send does not generate interrupts.
Instead I use polling right after I post to the send queue. Splitting
the CQ is also a preparation for using unsignaled send queue, this
significantly reducing the overhead of polling the CQ. As I mentioned,
this approach significantly improves small UDP messages send rate.