A survey of memory management techniques in virtualized systems

Abstract

Virtualization technology allows multiple operating systems to share hardware resources of a computer system in an isolated manner. Traditionally, memory is shared by an operating system using segmentation and paging techniques. With virtualization, memory partitioning and management has several new challenges. For isolated and safe execution, hypervisors do not provide direct access to hardware resources. Lack of direct access to the memory management hardware like page tables disqualifies direct usage of virtual memory solutions used on native (non-virtualized) setups. Further, aspects of dual control of the memory resource (by the guest OS and the hypervisor) and lack of semantics regarding memory usage in virtual machines present additional challenges for memory management. This paper surveys different techniques of memory partitioning and management across multiple guest OSs in a virtualized environment.An important goal of virtualization is to increase the physical machine utilization in order to save costs. With varying application demand for memory and diverse memory management policies of the guest OSs, ensuring optimal usage of memory is non-trivial. In this survey, challenges of memory management in virtualized systems, different memory management techniques with their implications, and optimizations to increase memory utilization are discussed in detail.