Re: [PATCH 01/10] IB/ehca: Support for multiple event queues

Roland Dreier [off-list ref] wrote on 16.07.2007 18:04:26:

It seems not quite right to me for the driver to advertise nr_eqs
completion vectors, but then if round-robin is turned on to ignore the
consumer's decision about which vector to use.

The round-robin feature was primarily meant as a debug/evaluation feature; 
it is not supposed to be active by default. ULP programmers can, for 
example, quickly evaluate the performance increase that comp_vectors could 
give them, without changing their code. Without this debug option, the 
comp_vector policy is still up to the ULPs.
 

Maybe if round-robin is turned on you should report 0 as the number of
completion vectors?

That sounds like a reasonable idea -- I'll change that right away.

Maybe the whole interface is broken and we should only be exposing
policies to consumers instead of the specific vector?

If so, I think the policies should be handled by the IB core code instead 
of being re-invented by each driver. The IB core would then again pass 
actual comp_vector values to the driver.
 

I think I would rather hold off on multiple EQs for this merge window
and plan on having something really solid and thought-out for 2.6.24.

It's your call, but the code is there and I don't expect it to change a 
lot later, so it could be used by others to get a first impression of 
what's possible using comp_vectors and to gather some experience with 
them.

Regards,
  Joachim