AUTHORS: Ahmad Afsahi and Nikitas J. Dimopoulos

TITLE:   Efficient Communication Using Message Prediction 
	 for Cluster of Multiprocessors


IN:      Fourth Workshop on Communication, Architecture, 
	 and Applications for Network-based Parallel Computing, 
	 CANPC'00, held in conjunction with the 6th International 
	 Symposium on High-Performance Computer Architecture, 
	 HPCA-6, Toulouse, France, January, 8, 2000.  

ABSTRACT

  With the increasing uniprocessor and SMP computation power available today,
interprocessor communication has become an important factor that limits 
the performance of caster of workstations. Many factors including 
communication hardware overhead, communication software overhead, and 
the user environment overhead (multithreading, multiuser) affect the 
performance of the communication subsystems in such systems.
  A significant portion of the software communication overhead belongs 
to a number of message copying. Ideally, it is desirable to have  a 
true zero-copy protocol where the message is moved directly from the 
send buffer in its user space to the receive buffer in the destination 
without any intermediate buffering. However, due to the fact that 
message-passing applications at the send side do not know the final 
receive buffer addresses, early arrival messages have to be buffered at 
a temporary area.
  In this paper, we show that there is a message reception communication 
locality in message-passing applications. We have utilized this 
communication locality and devised different message predictors at the 
receiver sides of communications. In essence, these message predictors can 
be efficiently used to drain the network and cache the incoming messages 
even if the corresponding receive calls have not been posted yet. The 
performance of these predictors in terms of hit ratio, on some parallel 
applications are quite promising and suggest that prediction has the 
potential to eliminate most of the remaining message copies.