out of memory can force aggressive cache behavior:

  cacheGC() -- do an incremental GC

  cacheFullSweep([dt]) -- Make a pass through objects in the cache
     removing unreferenced objects and, if dt > 0, deactivating
     objects accessed more than dt seconds ago.

  cacheMinimize([dt]) -- Make multiple passes through objects in the cache
     removing unreferenced objects and, if dt > 0, deactivating
     objects accessed more than dt seconds ago. Keep making passes
     until the cache size doesn;t change.