1. A computer program product, tangibly embodied in an information carrier, the computer program product comprising instructions operable to cause data processing apparatus to: compute a fill level of a cache memory, the cache memory being operable to store a plurality of entities; use a first eviction technique to evict one or more of the entities in the cache memory if the fill level exceeds a first threshold but not a second threshold; use a second, distinct eviction technique to evict one or more of the entities in the cache memory if the fill level exceeds the second threshold but not a third threshold; and decline subsequent requests to store additional entities in the cache memory if the fill level exceeds the third threshold.