Parallel Computer Architecture

5.5 Synchronization 349

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—ti—

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Array-based

LL-SC

LL-SC,

exponential

Ticket

Ticket, proportional ι

1 3 5 7 9 11 13 15 13 5 7 9 11 13 15 13 5 7 9 11 13 15

Number of processors Number of processors Number of processors

(a) Null (c = 0, d = 0) (b) Critical section (c = 3.64

ps,

d = 0) (c) Delay (c = 3.64 μ5, d =

1

.29 μ$)

FIGURE 5.30 Performance of locks on the SGI Challenge for three different scenarios

another processor can read the block across the bus. (The bias on the SGI Challenge

is actually more severe, since the releasing processor can satisfy its next read from its

write buffer even before the read exclusive corresponding