HyperAlloc: Efficient VM Memory De/Inflation via Hypervisor-Shared Page-Frame Allocators

The provisioning of the right amount of DRAM to virtual machines (VMs) is still a major challenge and cost driver in virtualization settings. Many VMs run applications with highly volatile memory demands, which either leads to massive overprovisioning in low-demand phases or poor QoS in high-demand phases. Memory hotplugging and ballooning have become established techniques (in Linux/KVM available via virtio-mem and virtio-balloon) to dynamically de/inflate the physical memory of a VM cooperatively, by having the guests give back unused memory to the hypervisor. However, current VM deflation techniques are either not DMA-safe, preventing the passthrough of important devices like GPUs or NICs, or are not flexible or fast enough to cope with the frequently changing demands of the guest.