Cache prefetching

Cache prefetching is a technique used by computer processors to boost execution performance by fetching instructions or data from their original storage in slower memory to a faster local memory before it is actually needed (hence the term 'prefetch'). Most modern computer processors have fast and local cache memory in which prefetched data is held till it is required. The source for the prefetch operation is usually main memory. Because of their design, accessing cache memories is typically much faster than accessing main memory, so prefetching data and then accessing it from caches is usually many orders of magnitude faster than accessing it directly from main memory.

There are three main metrics to judge cache prefetching

Coverage is the fraction of total misses that are eliminated because of prefetching, i.e

${\displaystyle Coverage={\frac {Cache\ Misses\ eliminated\ due\ to\ Prefetching}{Total\ Cache\ Misses}}}$,

where, ${\displaystyle Total\ Cache\ Misses=(Cache\ misses\ eliminated\ by\ prefetching)+(Cache\ misses\ not\ eliminated\ by\ prefetching)}$

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