Dynamic Memory Management For Virtual Machines Via Memory Hotplug

In a virtualized environment, memory is one of the most important resources that maysignificantly impact on the performance of virtual machines (VMs). The memory cap ofVM is often determinate before VM creating and cannot be changed during the life cycle ofVM. However, workloads running in VMs are dynamic and memory requirements are hardto predict. Therefore, some VMs may have insufficient memory and the others have lowmemory utilization with current static memory management. Memory can be efficientlyutilized only if memory requirements of different VMs can be satisfied on the fly. It isessential to improve memory management by dynamically adjusting the memory allocationof each VM.This paper presents DMM, a Dynamic Memory Management system based on Xen.DMM migrates Linux memory hotplug to paravirtualized virtual machine. It isimplemented by a device driver, which can dynamically extend memory address space andcause less memory fragmentations compared with balloon driver. With the change ofmemory utilization, DMM monitors memory information of all VMs and reasonablyreallocate memory among multiple VMs according to a memory allocation algorithm. It canbalance memory pressure among VMs, especially for the condition that there is little freememory available. In addition, if there is not enough memory to create new virtual machine,DMM overcommits memory by decreasing memory of current virtual machines to createnew virtual machine.The results show that DMM can efficiently utilize memory resource withoutconfronting the memory upper bound limitation. Moreover, the performance overhead isequivalent to balloon driver. The memory intensive workloads running in VM with DMMgains better performance than its running without DMM. DMM can create more VMsrunning in a physical machine to improve memory utilization.