Question

Explain the difference between temporal and spatial locality of reference

Answer 1

Answer:----------

Difference between temporal and spatial locality of reference:------------

Spatial locality:--------Spatial locality refers to the tendency of execution to involve a number of clustered memory locations. A program also tends to access data locations sequentially.

Temporal locality :----------Temporal locality refers to the tendency for a processor to access memory locations that have been used recently, eg when a loop is executed, the processor executes the same instructions repeatedly.

Good temporal locality ⇒ cache miss traffic decreases fast when cache size increases

Good spatial locality ⇒ cache miss traffic does not increase much when line size increases

HitA(M,L) – Hit rate (fraction of accesses that are cache hits) for sequence A of accesses for a (LRU, fully associative) cache of size M, with cache lines of length L (L divides M).

• MissA(M,L) = 1-HITA(M,L) – Miss rate
• MTA(M,L) = L × MissA(M,L) – Miss traffic

Good temporal locality = MTA(M,L) decreases fast when M increases
Good spatial locality = MTA(M,L) does not increase much when L increases (the miss rate decreases almost by a factor of L)