Writeinvalidate

Writeinvalidate is a term used in computer science to describe a cache coherence behavior and, in some contexts, a function or policy in caching libraries. It refers to the practice of invalidating cached copies of a data item when a write occurs to that item, rather than updating all caches with the new value.

In hardware and distributed systems, writeinvalidate is a coherence strategy employed to maintain consistency among multiple caches. When a processor or node writes to a shared memory location, other caches that hold copies of that location are sent invalidation messages. Those caches must fetch the updated data on subsequent access. This approach can reduce unnecessary write traffic and keep caches coherent, but may increase cache misses if many caches hold the same line and future reads require re-fetching data.

Writeinvalidate is often contrasted with update strategies, where caches receiving a write are proactively updated with the new value. The choice between invalidate and update depends on workload characteristics, such as write locality and read miss costs, as well as the underlying interconnect or directory-based directory coherence protocol.

In software development, writeinvalidate may appear as a cache invalidation operation or policy in caching frameworks, where a write to the underlying data store triggers invalidation of related cache entries to preserve correctness. It is one of several coherence strategies, alongside write-through and write-back approaches, and its effectiveness depends on system architecture and usage patterns.

See also: cache coherence protocols, MSI/MESI, write-through caches, write-back caches, cache invalidation.