Memory Pressure Balancing on Virtualized Servers

The effectiveness of a modern hyper visor on a virtualized server is measured by its consolidation ratio, which is defined as the maximum number of virtual machines (VM) that can run on a physical server without performance degradation. A key factor in determining a hyper visor´s consolidation ratio is its effectiveness in fairly distributing a virtualized server´s physical memory resource among the VMs running on it when the total memory demand of these VMs exceeds the server´s physical memory size. This paper describes the design, implementation and evaluation of a memory pressure balancer called Gatto that constantly measures the working set size of each VM running on a virtualized server, and exploits this information to distribute the server´s physical memory resource so as to balance the memory pressures experienced by these VMs. Gatto´s memory pressure balancing mechanism could be generalized and applied to achieve memory quality of service (QoS) guarantee onmultitenant virtualized servers.