[openib-general] MAD queuing model

[Michael S. Tsirkin]

Hello!
Quoting r. Sean Hefty (mshefty at ichips.intel.com) "Re: [openib-general] MAD queuing model":
> On Wed, 01 Sep 2004 15:30:38 -0400
> Hal Rosenstock <halr at voltaire.com> wrote:
> 
> > > If a work request for a MAD cannot be immediately posted to a QP, 
> > > should a call to ib_mad_post_send fail, or should the work request 
> > > be queued for later?  
> > 
> > It could be put on a deferred send queue that would be processed when
> > the next send completion occurs. This would make the access layer
> > implementation a little more complicated but save the client from
> > rerequesting.
> 
> I think we're in agreement that the access layer should perform the
> queuing, and that the queuing should be for actual work requests, which
> implies some of the internal layering of the code.
>

I'd like to propose a simpler approach: if the Q is full, drop
the MAD without any indication to the user (pretend the MAD was sent),
and let RMPP retry.

Note that you need retries anyway since the hardware is unreliable.

If the Q is big enough, this wont happend a lot, and its much simpler
I think than queueing in the layer.
MST