Hypervisor Balloon Memory Reset for Fragmentation Reduction

Solution Overview

Problem

Memory fragmentation occurs in virtual machines due to memory overcommit, leading to reduced system performance and stability, as the balloon driver controls memory addition and removal, scattering memory pages and preventing contiguous regions for reallocation, which complicates efficient memory management.

Innovation Solution

The hypervisor records the memory allocated by the device driver, locates contiguous regions of guest memory, reserves them, and notifies the guest OS, allowing for memory compaction and defragmentation upon reset, ensuring the guest OS operates with contiguous memory blocks and preventing crashes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the balloon driver controls memory addition and removal to enable memory overcommit, then memory utilization is improved, but memory fragmentation increases and contiguous regions for reallocation are lost

Engineering Contradiction:

Improvememory utilizationVSAvoidmemory fragmentation

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The hypervisor performs preliminary action by recording the amount of memory allocated by the device driver before resetting the virtual machine. This pre-recording enables the hypervisor to locate and reserve contiguous memory regions in advance, preventing memory fragmentation from occurring during the reset process while still allowing memory overcommit to function.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the memory management process into distinct phases: recording the allocated memory amount, locating contiguous regions, reserving those regions, and notifying the guest OS. This segmentation allows the hypervisor to manage memory allocation and contiguity separately from the balloon driver's memory addition/removal operations, resolving the contradiction between memory utilization and fragmentation.

Inventive Principle:

Principle #1Segmentation

2Productivity

If memory is reallocated by adding and removing memory from other virtual machines, then memory overcommit is achieved, but system performance and stability deteriorate due to fragmentation

Engineering Contradiction:

Improvememory overcommitVSAvoidsystem performance and stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The hypervisor performs preliminary action by recording the amount of memory allocated by the device driver before resetting the virtual machine. This pre-recording enables the hypervisor to locate and reserve contiguous memory regions in advance, preventing memory fragmentation from occurring during the reset process while still allowing memory overcommit to function.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The hypervisor uses feedback by notifying the guest OS that a contiguous region of guest memory addresses is reserved. This feedback mechanism allows the guest OS to adjust its memory operations accordingly, ensuring that memory is accessed in a contiguous manner that maintains system performance and stability while enabling memory overcommit.

Inventive Principle:

Principle #23Feedback

3Reliability

If the balloon driver controls how memory is added and removed to prevent guest OS instability, then reliability is improved, but memory pages are scattered and contiguous regions cannot be formed

Engineering Contradiction:

Improveguest OS stabilityVSAvoidmemory page contiguity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The hypervisor acts as an intermediary between the balloon driver and the guest OS. It records the memory allocation amount, locates contiguous regions, and reserves them before the guest OS resets. This intermediary role allows the balloon driver to control memory addition/removal for stability while the hypervisor ensures contiguity is maintained, resolving the contradiction between reliability and memory page contiguity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The hypervisor performs preliminary action by recording the amount of memory allocated by the device driver before resetting the virtual machine. This pre-recording enables the hypervisor to locate and reserve contiguous memory regions in advance, preventing memory fragmentation from occurring during the reset process while still allowing memory overcommit to function.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11474852B2Resetting persistent balloon memory for fragmentation reduction

Publication Date: 2022.10.18 RED HAT INC

AI summary

A balloon memory fragmentation reduction system includes a memory, at least one processor in communication with the 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 record an amount of memory allocated by the device driver of the guest OS, locate a contiguous region of guest memory addresses according to the amount of memory allocated by the device driver, reserve the contiguous region of guest memory addresses, and notify the guest OS that the contiguous region of guest memory addresses is reserved.