1. A method of managing a computer memory by selectively admitting new objects into the memory, comprising: receiving a request for an object not stored in the memory; storing the object in the memory if it has previously been requested a designated number of times; storing the object in the memory if its size satisfies a size criterion; and evicting, as may be necessary in connection with storing a not-previously-requested object having a size satisfying the size criterion, one or more currently stored objects.