[openib-general] basic IB doubt

[Sean Hefty]

>> Polling on a CQ involves a function call, synchronization to the CQ, and
>> formatting a structure to return to the user.  I don't see this ever being
>> faster than polling memory.
>
>Why don't you measure it, then?

Why?  Reading a memory location directly will be faster than calling a function
to read from a memory location.

>For example, an iWarp implementation
>is going to be slowed down if it has to reorder segments to deliver
>the last byte last. This expense might be more than the function call.

It only needs to defer the last byte.  The claim being made is that the last
byte will be delivered last.

Yes, I can implement something non-performant in this mode, but that doesn't
invalidate polling memory as a general solution.

>You're also assuming that programs are only checking the last byte of
>the buffer.

The applications I care about are polling on the last byte.

- Sean