Parallel Computer Architecture

858

CHAPTER

11 Latency Tolerance

The potential performance disadvantages

of

using block transfer

are

■ Higher

overhead

per transfer

m Increased contention. Long messages tend

to

incur higher contention, both

at

the endpoints

and in the

network, because they occupy more resources

in the

network

at a

time:

the

latency tolerance they provide places greater bandwidth

demands

on the

communication architecture.

On the

other hand, bandwidth

demand

due to

protocol messages

is

reduced compared

to a

cache coherence

protocol,

as

discussed earlier.

■ Extra work. Programs

may

have

to do

extra work

to

organize themselves

so

communication

can be

performe