Proactively Breaking Large Pages to Improve Memory Overcommitment Performance in VMware ESXi
Fei Guo, Seongbeom Kim, Yury Baskakov, Ishan Banerjee · 2015
VMware ESXi leverages hardware support for MMU virtualization available in modern Intel/AMD CPUs. To optimize address translation performance when running on such CPUs, ESXi preferably uses host large pages (2MB in x86-64 systems) to back VM's guest memory. While using host large pages provides best performance when host has sufficient free memory, it increases host memory pressure and effectively defeats page sharing. Hence, the host is more likely to hit the point where ESXi has to reclaim VM memory through much more expensive techniques such as ballooning or host swapping. As a result, using host large pages may significantly hurt consolidation ratio.