[ofiwg] send/recv "credits"

[Sur, Sayantan]

> > How would this usage model differ significantly from the data transfer call
> > simply returning FI_EGAIN?
> 
> The difference is in app usage model - typical is:
> If (credits_available) {
>   Do_prep_work();
>   Post_send();
> } else {
>   Queue_for_later();
> }
> 
> With the EAGAIN model, this has to change to the potentially less efficient :
> Do_prep_work();
> If (post_send() != OK) {
>   Undo_prep_work();
^^^^^^
>   Queue_for_later();
> }
> 

Jumping in late on this thread. Not all apps need to undo work if send credits are not available. i.e.

Prep = Do_prep_work();
If (post_send() != OK) {
	Queue_for_later(prep);
}

MPI for example can follow this model.

Sayantan.