Dynamic paging method switching - An implementation for KVM

Abstract

The increasing adoption of virtualization in high-performance computing domain makes it necessary to reduce the performance loss due to virtualization for the workloads. In a single computing node, the loss is mainly incurred by memory virtualization. To take the advantages of virtual memory, page tables are commonly adopted for the mapping from virtual to physical address in operating systems. To take the advantages of system virtualization, page tables are also adopted for the mapping from guest virtual to host physical address. The two standard approaches are shadow and nested page tables. As each of them has its strengths and weaknesses, neither can simply be replaced by the other. An optimal practice is to exploit these strengths as the workload is always changing. However, the current hypervisors cannot do this due to the static way of configuring the paging method. This paper proposes and realizes DPMS - a variant of the idea “dynamic page method switching” in the context of KVM. DPMS is able to detect the workload type and adjust the page method accordingly. Benchmark results show that DPMS yields the best performance compared with the shadow and nested paging for almost all the tested workloads.