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Cache Miss

An event where the data requested by the CPU is not found in the cache memory, requiring a slower access to main memory.

Categoryhardware

Overview

Cache misses are a major source of performance degradation. When a miss occurs, the CPU must stall or perform other work while the data is retrieved from the much slower RAM (or even disk).

Types of Misses (The 3 Cs)

  1. Compulsory: The first time a piece of data is accessed (unavoidable).
  2. Capacity: The cache is too small to hold all the data the program needs.
  3. Conflict: Multiple memory locations map to the same cache line (in set-associative caches).

Impact

A cache miss can take hundreds of clock cycles, whereas a cache hit takes only a few.

Related Terms

Cache Hit