Memory Ballooning


Memory ballooning is a technique used in virtualization environments to efficiently allocate and manage memory resources between multiple virtual machines (VMs) running on a single host. It allows the hypervisor to dynamically adjust the amount of memory allocated to a VM by reclaiming unused memory from a VM and redistributing it to others that need it more. This process optimizes memory usage and helps prevent memory over-commitment, ensuring better performance and resource utilization for all VMs on the host.

Key Takeaways

  1. Memory ballooning is a virtualization technique that allows a hypervisor to manage the amount of physical memory allocated to virtual machines (VMs) by dynamically adjusting it based on their current needs.
  2. The technology helps optimize memory usage and resource allocation between VMs, leading to improved performance and efficiency in the virtualized environment.
  3. Memory ballooning requires support from the guest operating system’s balloon driver and the hypervisor to communicate and cooperate effectively for seamless memory adjustments.


Memory ballooning is an important technology term because it pertains to the efficient and dynamic management of virtual machine memory resources within a host system.

This technique allows virtual machines to effectively “borrow” or “release” memory space on as-needed basis without affecting their overall performance.

Memory ballooning helps improve the utilization of available resources, enabling the host to allocate and distribute memory more efficiently across multiple VMs.

By maximizing resource utilization, memory ballooning ensures that virtual machines operate smoothly without sacrificing performance, thereby lowering costs and enhancing scalability within virtualized environments.


Memory ballooning is a technique used primarily in virtualization environments to optimize the distribution of memory resources among multiple virtual machines (VMs) running on a single physical host. The primary purpose of memory ballooning is to ensure efficient utilization of the host’s memory by dynamically reallocating portions of it to VMs that require more resources at any given time. This dynamic reallocation allows for higher consolidation ratios, as more virtual machines can be run on a single host without overcommitting the host’s memory resources.

Consequently, it reduces operational costs and energy consumption while also improving the overall performance of the virtualization environment. Memory ballooning works through the use of a balloon driver that is installed in each VM’s guest operating system. The hypervisor, which is responsible for managing the host’s resources, communicates with the balloon driver to either inflate (increase memory allocation) or deflate (decrease memory allocation) the VM’s memory based on their current demands.

When a VM requires more memory, the balloon driver inflates the balloon, requesting unused memory from the VM and making it available to other VMs that need it. Conversely, when a VM’s memory demand decreases, the balloon driver deflates, releasing the previously allocated memory back to the guest operating system. By doing so, the memory resources are efficiently managed and distributed among all VMs running on the host, ensuring optimal performance and avoiding potential bottlenecks or crashes caused by memory overcommitment.

Examples of Memory Ballooning

Memory ballooning is a technique used in virtualization environments to efficiently manage the memory resources of multiple virtual machines (VMs) running on a single physical host. Here are three real-world examples of memory ballooning:

VMware vSphere: VMware’s virtualization platform, vSphere, features the VMware Balloon Driver, a mechanism that helps manage and allocate memory dynamically between the VMs running on the host system. This driver, when installed in the VM’s operating system, allows the hypervisor to request the VM to release memory using the balloon driver when the host has limited available resources.

Proxmox Virtual Environment (PVE): Proxmox’s open-source server virtualization management platform utilizes the Linux kernel-based virtual machine (KVM) and memory ballooning to allocate and manage memory across running VMs. Ballooning in Proxmox allows the host to “borrow” unused memory from one VM and give it to another VM in need of more memory, ensuring efficient memory usage among the virtualized machines.

VirtualBox: Oracle’s open-source virtualization software, VirtualBox, also uses a form of memory ballooning to manage memory for its virtual machines. The guests on a VirtualBox host can adjust their memory usage dynamically using the VBEMP (VirtualBox Guest Memory Paging) feature, which allows the host to share available memory effectively between the VMs without interrupting their operation.

FAQ: Memory Ballooning

What is memory ballooning?

Memory ballooning is a technique used by virtualization systems to efficiently allocate and manage memory resources between multiple virtual machines running on a single physical host. It allows the hypervisor to temporarily reclaim unused memory from one VM and allocate it to another VM that requires more memory at a given time.

How does memory ballooning work?

In a virtualized environment, the hypervisor monitors the memory usage of each virtual machine and identifies when memory is not being fully utilized. It then inflates a “balloon” within the guest OS, which consumes the unused memory, effectively freeing it up for other VMs. This process is dynamic, allowing the hypervisor to reallocate memory as needed when the usage pattern changes within the virtual machines.

What are the benefits of memory ballooning?

Memory ballooning helps in optimizing physical memory usage by redistributing unused memory among virtual machines on a host. VMs often allocate more memory than they actually use, so memory ballooning helps make better use of available resources, leading to improved performance and reduced hardware costs, as more virtual machines can be run on a single physical host.

Are there any drawbacks to memory ballooning?

While memory ballooning provides several benefits, it can also have some drawbacks if not properly managed. When the balloon driver inflates to reclaim memory, it may cause performance issues within the guest operating system as it competes for resources with other processes and applications. Additionally, if the hypervisor continually reclaims and reallocates memory in short periods of time, it may cause significant performance overhead.

Is memory ballooning supported by all hypervisors?

Most popular hypervisors, such as VMware ESXi, Microsoft Hyper-V, and KVM, support memory ballooning. However, the implementation and features may vary between different platforms. It’s essential to consult the documentation of your specific hypervisor to understand its capabilities and ensure proper configuration for optimal performance.

Related Technology Terms

  • Dynamic Memory Allocation
  • Memory Overcommitment
  • Guest Operating System
  • Host Resource Management
  • Memory Swapping

Sources for More Information

  • VMware: This company is a leading provider of virtualization and cloud computing solutions. They offer extensive documentation on memory ballooning to manage memory resources in virtual machines.
  • Red Hat: As a major player in the open-source software community, Red Hat provides valuable resources on memory ballooning and its utilization in their virtualization and cloud products.
  • IBM: IBM, a multinational technology company, has a rich repository of knowledge on memory ballooning and other advanced technologies, making it a reliable source for understanding and implementing memory ballooning.
  • Microsoft: Microsoft offers numerous resources on memory ballooning in the context of their Hyper-V virtualization platform and other related products.

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