Chapter 6 Memory Hierarchy --- Locality

概念：

Locality is typically described as having two distinct forms: temporal locality and spatial locality .

In aprogram with good temporal locality, a memory location that is referenced once is likely to be referenced
again multiple times in the near future.

In a program with good spatial locality, if a memory location is
referenced once, then the program is likely to reference a nearby memory location in the near future.

 

重要性：

Programmers should understand the principle of locality because, in general, programs with good locality
run faster than programs with poor locality

 

 

 

Summary of Locality
In this section we have introduced the fundamental idea of locality and we have identified some simple rules
for qualitatively evaluating the locality in a program:

1. Programs that repeatedly reference the same variables enjoy good temporal locality.
2.  For programs with stride-k reference patterns, the smaller the stride the better the spatial locality. Programs
with stride-1 reference patterns have good spatial locality. Programs that hop around memory
with large strides have poor spatial locality.

3. Loops have good temporal and spatial locality with respect to instruction fetches. The smaller the
loop body and the greater the number of loop iterations, the better the locality.