Memory resource management in VMware ESX server

TLDR

VMware ESX Server is a thin software layer that multiplexes hardware resources among virtual machines running unmodified commodity operating systems. This paper introduces several novel ESX Server mechanisms and policies for managing memory. The authors employ ballooning to reclaim least valuable pages, an idle memory tax to balance utilization and isolation, and content‑based page sharing with hot I/O page remapping to eliminate redundancy and reduce copying overhead. These techniques together enable efficient support of virtual machine workloads that overcommit memory.

Abstract

VMware ESX Server is a thin software layer designed to multiplex hardware resources efficiently among virtual machines running unmodified commodity operating systems. This paper introduces several novel ESX Server mechanisms and policies for managing memory. A ballooning technique reclaims the pages considered least valuable by the operating system running in a virtual machine. An idle memory tax achieves efficient memory utilization while maintaining performance isolation guarantees. Content-based page sharing and hot I/O page remapping exploit transparent page remapping to eliminate redundancy and reduce copying overheads. These techniques are combined to efficiently support virtual machine workloads that overcommit memory.