Yes, but most workloads are fairly unprepared for this sadly. And they're really not ready for memory unplug. (I also miss the days of my multi socket boxes and plugging in CPUs and memory).
What do VM-guest memory-ballon drivers do right now when the host suddenly attempts to reserve more memory than the guest has free? I'd presume the kernel would just consider itself to be in an OOM condition, and start killing processes to free up the memory until it can return OK to the balloon driver, no?
Because, from what I understand, that's closer to the scenario we're talking about here: you're not abruptly yanking DIMMs (like physical memory hotplug); rather, you (the hypervisor) are gracefully letting the guest know that some memory is about to go away, and since you (the hypervisor) have your own virtual TLB, you can let the guest OS decide which "physical" memory (from its perspective) is going away, before it happens.
Yes, but most workloads are fairly unprepared for this sadly. And they're really not ready for memory unplug. (I also miss the days of my multi socket boxes and plugging in CPUs and memory).