Virtual Machine Memory Overcommit via Reverse Ballooning

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Solution Overview

Problem

Existing virtual machine memory overcommit techniques, such as balloon drivers, face challenges in preventing guests from prematurely using more memory than allocated, leading to system performance issues and resource inefficiencies, especially when initialization is delayed or disabled.

Innovation Solution

The implementation of reverse ballooning, where initialization memory is exposed to the guest OS, and device memory is managed by a device driver to query and report available memory, preventing premature usage and allowing the hypervisor to reclaim unused memory for reallocation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If balloon drivers are used for memory overcommit, then memory can be reclaimed from guests, but guests may prematurely use more memory than allocated causing system performance issues

Engineering Contradiction:

Improvememory reclamationVSAvoidmemory allocation control

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The balloon driver is initialized during guest OS boot sequence before the guest can access or allocate memory. This preliminary initialization ensures the driver is ready to control and reclaim memory before the guest OS can prematurely use more memory than allocated, preventing system performance issues while enabling memory reclamation

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If balloon driver initialization is delayed or disabled, then guest can access memory freely, but the guest may use more memory than permitted requiring hypervisor intervention

Engineering Contradiction:

Improvememory accessVSAvoidmemory overuse

Core Design Contradiction:

Ease of operationVSQuantity of substance

Solution Approach 1:

The balloon driver performs preliminary anti-action by establishing memory control mechanisms during guest OS initialization. This preemptive control prevents the guest from using more memory than permitted, eliminating the need for later hypervisor intervention while maintaining free memory access within allocated limits

Inventive Principle:

Principle #9Preliminary anti-action

3Reliability

If hypervisor allocates more memory to prevent guest crashes, then system resource utilization decreases, but guest stability improves

Engineering Contradiction:

Improveguest stabilityVSAvoidsystem resource utilization

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The balloon driver implements feedback mechanisms that continuously monitor guest memory usage and communicate with the hypervisor. This feedback loop allows the hypervisor to maintain guest stability through controlled memory allocation while optimizing system resource utilization by reclaiming unused memory, preventing unnecessary memory over-provisioning

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10417047B2Virtual machine memory overcommit by reverse ballooning

Publication Date: 2019.09.17 RED HAT INC

AI summary

A virtual machine memory overcommit system includes an initialization memory, a device memory, at least one processor in communication with the initialization memory and the device memory, a guest operating system (OS) including a device driver, and a hypervisor executing on the at least one processor. The hypervisor is configured to expose the initialization memory to the guest OS of a virtual machine, initialize the guest OS, and expose the device memory to the guest OS. The device driver is configured to query an amount of memory available from the device memory and report the amount of memory available to the guest OS.