Systems and techniques for dynamic selection of policy that determines whether copies of shared cache lines in a processor core complex are to be stored and maintained in a level 3 (L3) cache of the processor core complex are based on one or more cache line sharing parameters or based on a counter that tracks L3 cache misses and cache-to-cache (C2C) transfers in the processor core complex, according to various embodiments. Shared cache lines are shared between processor cores or between threads. By comparing either the cache line sharing parameters or the counter to corresponding thresholds, a policy is set which defines whether copies of shared cache lines at such indices are to be retained in the L3 cache.