Browse Prior Art Database

Method and Algorithm for an Extended Virtual Memory System for Mobile Devices

IP.com Disclosure Number: IPCOM000010146D
Original Publication Date: 2002-Oct-25
Included in the Prior Art Database: 2002-Oct-25
Document File: 5 page(s) / 48K

Publishing Venue

Motorola

Related People

John Richard Kane: AUTHOR [+2]

Abstract

Mobile devices such as cell phones are increasingly using memory intensive applications and media files. Sufficient storage will not exist on most devices to accommodate users’ desires. We describe a virtual memory system that splits the user file system across the mobile device and a secondary storage system while presenting a complete view of the file system and sufficient status and user interface activity to allow the user to exert control over the memory management operations as well as understand the implications of latency and cost for moving memory segments from secondary storage into physical memory. The system components to implement this method of operation are described as well as an algorithm for removal of memory segments to make room for a new file loaded from secondary storage.

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Method and Algorithm for an Extended Virtual Memory System for Mobile Devices

John Richard Kane and Michael D. Pearce

Abstract:

Mobile devices such as cell phones are increasingly using memory intensive applications and media files.  Sufficient storage will not exist on most devices to accommodate users’ desires.  We describe a virtual memory system that splits the user file system across the mobile device and a secondary storage system while presenting a complete view of the file system and sufficient status and user interface activity to allow the user to exert control over the memory management operations as well as understand the implications of latency and cost for moving memory segments from secondary storage into physical memory.  The system components to implement this method of operation are described as well as an algorithm for removal of memory segments to make room for a new file loaded from secondary storage.

Problem:

Users want to carry and use many media elements and applications on their mobile devices.  Most times the user’s capacity demands exceed the device’s storage capabilities.  This is particularly true of low cost cellular telephones.  Part of our solution is to support a user memory or file system that holds all user data but distributes this data across physical memory in the mobile device and a secondary storage system remote from the device.  A traditional approach to this problem in computer systems has been to implement a virtual memory or virtual file system that transparently moves data between local and secondary memory.  This has been done with sufficient speed that the operation is transparent to the user and applications.  The secondary storage system and access thereof is such that transparent virtual memory or file system operation as disclosed in the literature is inappropriate for mobile devices due to latency over wireless communication channels. 

Therefore the envisioned solution must enlist some amount of user interaction and interface control.  If the system is to rearrange memory to support a “virtual” storage system for the mobile device, the user must be informed of the actions and participate in such decisions.  This is motivated both by the potential latency of the operation and by the potential costs incurred in network traffic.  We disclose a method and algorithms for the implementation of such a virtual memory system enlisting user interactions.

Basis of the solution:

The solution implements a virtual memory system on the mobile device.  Its components are shown in Figure 1.  We define:

  • A primary and secondary storage system for the device, with the secondary storage being either network accessible via a communications channel (preferred implementation) or removable media where the communication channel is an internal bus (or combo of both)
  • A virtual memory controller that moves and manages memory segments between the physical memory of the mobile device and the secondary storage s...