Hi, I'm experiencing sluggish UI change with my retina macbook pro, upon checking Active Monitor, it seems I'm running out of memory. Whats puzzling is the OS holding on to 2GB of ram as inactive memory even when the hard drive is been used as virtual memory. My understing is the OS should free up inactive memory as free memory runs out. So why would the OS not release the extra memory? It this a Mountain Lion bug or some kind of design feature I'm not aware of? Many thanks P.S. How come the VM size is 384GB when the hard drive is only 256GB?