Structuring Communication
Given amount of comm, goal is to reduce cost
Cost of communication as seen by process:
C = f * ( o + l + + tc - overlap)
- f = frequency of messages
- o = overhead per message (at both ends)
- l = network delay per message
- nc = total data sent
- m = number of messages
- B = bandwidth along path (determined by network, NI, assist)
- tc = cost induced by contention per message
- overlap = amount of latency hidden by overlap with comp. or comm.
- Portion in parentheses is cost of a message (as seen by processor)
- ignoring overlap, is latency of a message
- Goal: reduce terms in latency and increase overlap