Least-recently-used (LRU) to first-dirty-member distance-maintaining cache cleaning scheduler

A technique for scheduling cache cleaning operations maintains a clean distance between a set of least-recently-used (LRU) clean lines and the LRU dirty (modified) line for each congruence class in the cache. The technique is generally employed at a victim cache at the highest-order level of the cache memory hierarchy, so that write-backs to system memory are scheduled to avoid having to generate a write-back in response to a cache miss in the next lower-order level of the cache memory hierarchy. The clean distance can be determined by counting all of the LRU clean lines in each congruence class that have a reference count that is less than or equal to the reference count of the LRU dirty line.