The fact that only 256GB of 1TB memory is actively used does not mean it hasn’t been allocated? If it has been allocated, which means it is in use somehow, then we cannot just randomly give it away to someone else. If we want to free up the block we need to use a memory reclamation technique, which are the ones I mention above.
Active = ”Amount of memory that is actively used, as estimated by VMkernel based on recently touched memory pages.”
With “recent” in esxtop referring to the last 5 seconds.