LRUähnlich

LRUähnlich (LRU-like) denotes a family of cache replacement policies that approximate the Least Recently Used (LRU) strategy without requiring a precise, full ordering of items by recency. While exact LRU maintains a strict timeline of accesses for all cached items, LRUähnliche methods reduce metadata and computation by relying on approximate recency information. They aim to balance hit rate with implementation simplicity and cost.

Common approaches include CLOCK (second-chance), a practical approximation that uses a circular list and a single reference bit per item; aging schemes that periodically shift a per-item counter to reflect older usage; and LRU-k variants that look at the k-th most recent reference to estimate how recently an item has been used. Multi-queue and adaptive replacement caches (ARC and related schemes) also embody LRU-like behavior by separating recency and frequency information and adapting eviction decisions to workload characteristics.

LRUähnlich policies are widely used in CPU data caches, memory paging in operating systems, database buffer caches, and web caching. They generally offer good performance for workloads with temporal locality while keeping metadata overhead lower than exact LRU. However, because they do not track every access with perfect precision, eviction decisions can be suboptimal for certain workloads, potentially reducing hit rates compared with true LRU at comparable cost.

In practice, the choice of LRUähnlich policy depends on hardware constraints, workload, and acceptable trade-offs between accuracy and metadata overhead.