The test-and-set spin lock is the simplest synchronization mechanism possible on most commercial shared-memory machines. This spin
Question:
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Unlocking a spin lock simply requires a store of the value 0.
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As discussed in Section 4.7, the more optimized test-and-test-and-set lock uses a load to check the lock, allowing it to spin with a shared variable in the cache.
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Assume that processors P0, P1, and P15 are all trying to acquire a lock at address 0x100 (i.e., register R1 holds the value 0x100). Assume the cache contents from Figure 4.37 and the timing parameters from Implementation 1 in Figure 4.38. For simplicity, assume the critical sections are 1000 cycles long.
a. Using the test-and-set spin lock, determine approximately how many memory stall cycles each processor incurs before acquiring the lock.
b. Using the test-and-test-and-set spin lock, determine approximately how many memory stall cycles each processor incurs before acquiring the lock.
c. Using the test-and-set spin lock, approximately how many bus transactions occur?
d. Using the test-and-test-and-set spin lock, approximately how many bus transactions occur?
Step by Step Answer:
a Assume the processors acquire the lock in order P0 will acquire it first incurring 100 stall cycles to retrieve the block from memory P1 and P15 will stall until P0s critical section ends pingpongin...View the full answer
Computer Architecture A Quantitative Approach
ISBN: 978-0123704900
4th edition
Authors: John L. Hennessy, David A. Patterson
