Topics on KVM

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Topics on KVM

• Presented By
• Xiaozhou David Zhu

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Topics covered

• Introduction
• Java2 Platform Micro Edition
• CLDC
• KVM

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Introduction

• Everything will be connected to the Internet
• Customizable, Personal Services
• By downloading new services and applications from
  the internet
• Currently, interactive games, banking and
  ticketing applications, as shown in next slide.

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Introduction

• Technology that enables this Java2 Platform
  Micro Edition (J2ME)
• J2ME Configurations and Profiles
• Three layers of software built upon the Host
  Operating System of the device
• JVM Layer
• Configuration Layer
• Profile Layer

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J2ME

• J2ME Devices
• J2ME Building Blocks
• Configurations
• Profiles

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J2ME Devices

• J2ME keeps key features of Java Technology
• Built-in consistency run anywhere, any time, on
  any device
• High-level OOP
• Portability of code
• Safe network delivery
• Upward scalability with J2SE and J2EE

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J2ME Device cont.

• 2 broad categories of products
• Shared, fixed, connected information devices
  (represented by CDC) Memory budget 2-16 MB,
  most often using TCP/IP
• Personal, mobile, connected information devices
  (represented by CLDC) memory budget about
  128KB, low bandwidth, intermittent network
  connections, often not based on TCP/IP

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J2ME Building Blocks

• Configuration
• Defines a minimum platform for a horizontal
  category or grouping of devices, each with
  similar requirements on a total memory budget and
  processing power.
• Profile
• Is layered on top of a configuration. It
  addresses the specific demands of a certain
  vertical device family. It guarantees
  interoperability within a family or domain.

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J2ME Profile

• Defines Java platforms for specific vertical
  markets
• Consumers would expect useful applications to be
  portable within a device family.
• Portability across different device categories is
  not necessarily very important.
• Example cell phones, washing machines,
  intercommunicating electronic toys, all belong to
  different device family, even though there might
  be many different models within each family.

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J2ME Profile cont.

• Portability requirements profiles serve
• Complete toolkit for implementing applications
  for a particular kind of device
• A profile ma also be created to support a
  significant, coherent group of applications that
  might be hosted on several categories of devices.

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J2ME Configurations

• In J2ME, an application is written for a
  particular profile, and a profile is based upon
  or extends a particular configuration. Thus all
  of the features of a configuration are
  automatically included in the profile and may be
  used by applications written for that profile.
• A configuration defines a Java platform for a
  horizontal category or grouping of devices with
  similar requirements on total memory budget and
  other hardware capabilities.

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J2ME Configurations cont.

• A configuration specifies
• Language features supported
• JVM features supported
• Basic Java libraries and APIs supported
• A configuration is a contract between a profile
  implementer and a devices JVM, thus portability
  is achieved.

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J2ME Configurations cont.

• To avoid fragmentation, only 2 standard J2ME
  configurations are defined
• CLDC
• Very closely related to KVM CLDC is the
  specification for a class of JVM that can run
  on the categories of devices, and KVM is a
  particular implementation of a JVM meeting the
  CLDC specifications.
• CDC shall be a superset of CLDC, as shown in the
  next slide

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CLDC

• The details of CLDC can be found in the white
  paper. I only cover the goals for CLDC
• To define a standard Java platform for small,
  resource-constrained, connected devices.
• To allow dynamic delivery of Java applications
  and content to those devices.
• To enable 3rd party application developers to
  easily created applications and content tat can
  be deployed to those devices.

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The K Virtual Machine (KVM)

• KVM is a compact, portable JVM intended for
  small, resource-constrained devices such as cell
  phones, pagers, etc.
• The high-level design goal for KVM was to create
  the smallest possible complete JVM that would
  maintain all the central aspects of the Java
  programming language, and that would nevertheless
  run in a resource-constrained device with only a
  few tens or hundreds of KB of available memory
  (hence the name K, for Kilobytes)

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KVM cont.

• KVM is designed to be
• Small, with a static memory footprint of the VM
  core in the range 40 to 80 KB
• Clean and highly portable
• Modularand customizable
• As complete and fast as possible without
  sacrificing the other design goals.

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KVM implementation

• KVM is implemented in C
• Suns KVM can be compiled and tested on Solaris
  and Windows, as well as on Palm OS
• Has been ported to over 25 devices

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KVM compilation

• Can built with any C compiler capable of
  compiling ANSI-compliant C files, the only
  non-ANSI feature in the source code is its use of
  64-bit integer arithmetic
• Compiler supported
• Metrowerks CodeWarrior Rel. 6 for Palm
• Sun DevPro C Compiler 4.2 on Solaris
• GNU C compiler on Solaris
• Microsoft VC 6.0 Pro on Win 98 and NT4.0

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KVM Porting KVM Code

• The majority of KVM source code is common to all
  implementations.
• Machine-dependent, platform-specific code is
  isolated to small number of files.
• New or modified versions of these files must be
  created for each port.
• Some runtime functions must be implemented to
  provide the necessary interface between KVM and
  underlying native operating environment init,
  finalize, heap allocation/deallocation, fatal
  error reporting, event handling, current time,
  etc.

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Launching the KVM

• On desktop run form the command line
• On devices with user interface capable of
  launching native applications (Palm OS) the KVM
  code can be configured to run in that fashion
• For other devices, KVM code provides a reference
  implementation of facility called the Java
  Application Manager (JAM) to serve as an
  interface between host OS and the VM

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KVM other details

• Class Loading
• From a directory path as well as from a JAR (Java
  Archive) file
• 64-bit support
• Macros are provided that can be redefined to
  perform the apporopriate opeartions for compilers
  that do not support 64-bit integers.
• Native Code
• Any native code called must be linked at compile
  time, invoking native method is via native method
  lookup tables created during build process.

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KVM other details, cont.

• Event Handling 4 ways
• Synchronous notification (blocking)
• Polling in Java code
• Polling the bytecode interpreter
• Asynchronous notification

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KVM other details, cont.

• Classfile verification use stackmap
• Each method in a downloaded Java classfile
  contains a stackmap attribute, which is added to
  standard classfile by a pre-verfication tool
  that analyzes each method in the classfile.
• Typically performed on a server or desktop before
  the classfile is downloaded to the device.
• Faster, lessVM code and DRAM consumption than
  standard JVM verification step, but with same
  level of security.

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KVM Java Code Compact

• JCC, Also known as ROMize
• Allows Java classes to be linked directly in the
  VM, reducing VM startup time considerably.
• Combine multiple input files
• Determine an object instances layout and size
• Load only designated class members, discarding
  others.
• JCC tool is written in Java, so is portable to
  various development platforms.

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Reference

• White Paper from Sun.com
• (http//java.sun.com/products/cldc/wp/KVMwp.pdf)
• Some useful links to KVM
• (http//webdev.apl.jhu.edu/rbe/kvm/)
• which links to several other links.