New MCA parameter: btl_usnic_ack_iteration_delay. Set this to the
number of times through the usNIC component progress function before
sending a standalone ACK (vs. piggy-backing the ACK on any other send
going to the target peer).
Use "ticks" language to clarify that we're really counting the number
of times through the usNIC component DATA_CHANNEL completion check (to
check for incoming messages) -- it has no relation to wall clock time
whatsoever.
Also slightly change the channel-checking scheme in usNIC component
progress: only check the PRIORITY channel once (vs. checking it once,
not finding anything, and then falling through the progress_2() where we
check PRIORITY again and then check the DATA channel).
As before, if our "progress" libevent fires, increment the tick
counter enough to guarantee that all endpoints that need an ACK will
get triggered to send standalone ACKs the next time through progress,
if necessary.
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
(cherry picked from commit 968b1a51b59898877a8c7268d463d3d7d78d86a3)
b5cb03450c