Memory Hierarchy
What is the main effect of a victim cache, a small fully associative buffer that temporarily holds lines evicted from the L1 cache?
- ALines reused right after eviction can be recovered quickly, reducing the cost of conflict misses
- BIt reduces capacity misses as much as enlarging the L1 cache would
- CIt eliminates compulsory misses and makes prefetching unnecessary
Show answer and explanation
Answer: A. Lines reused right after eviction can be recovered quickly, reducing the cost of conflict misses
In direct-mapped and similar caches, data competing for the same set evicts each other, and a just-evicted line is often needed again soon. A victim cache holds a few to a dozen or so evicted lines, so an L1 miss that finds the line there is served faster than from the next level. Being small, it does little for capacity misses, and it cannot help compulsory misses for data never loaded.
- A. Correct. It rescues reuse right after eviction, cutting the cost of conflict misses.
- B. It holds only a handful of lines, so its effect on capacity misses is small.
- C. It cannot help data that was never loaded.