Most implementations of Java technology have been too slow, too big, or too unreliable for use in Internet appliances and embedded devices. Insignia Solutions' Jeode platform improves Java functionality for these resource-constrained devices, allowing you to create and deploy Java-based applications.

The Jeode platform offers the following tools:

• A full-featured implementation of the PersonalJava and EmbeddedJava specifications that passed the PersonalJava and EmbeddedJava compatibility test suites to become a "Sun-Authorized Virtual Machine"
• Accelerated performance, robustness, and efficient memory utilization
• Configurability and tunability to meet the needs of Internet appliance and embedded device developers
• A turn-key solution ported and tested on a variety of processors
• Support, training, consulting, customization, and development tools.

The Jeode platform is integrated with a suite of tuning and programming tools to help you write and implement Java programs. The suite includes the Jeode Embedded Virtual Machine (EVM) and the latest PersonalJava (including AWT) or EmbeddedJava class libraries. It offers tools for editing, compiling, and browsing Java applications as well as runtime debug utilities, a source level debugger, configurator, monitor, and a memory-use analyzer.

Figure 1: Java development tool function path. Java is translated to native code using one of two resources (either a compiler or an interpreter), depending on if the code path is used frequently or rarely, in order to conserve the device resources.

The platform allows you to use the tools of your choice to edit, compile, browse, and debug Java application through the host computer. Special integration exists between the Jeode platform and Metrowerks' CodeWarrior Integrated Development Environment (IDE). A CodeWarrior plug-in is provided as part of the Jeode installation, offering EVM-specific functionality. Standard interfaces, such as JVMDI/JDWP, are also supported.

The EVM is a full-featured Java-compatible virtual machine and supports embedded class libraries that are compatible with 1.1.1 PersonalJava and 1.0.3 EmbeddedJava specifications (roughly equivalent to 1.1.7b JDK).

Most implementations of the Java platform are interpreted and therefore are too slow for many Internet appliances and embedded devices. Just-in-time (JIT) compilation technology is suitable for the desktop environment but is inappropriate for Internet appliance and embedded classes of devices. Typical JIT implementations require large amounts of memory, disk storage, and virtual memory for paging segments of dynamically compiled code. JIT compilers can also cause unpredictable delays during compilation and consume an unbounded amount of physical and virtual memory.

Figure 2: Unlike JIT compilation technology, adaptive dynamic compiling conserves memory and time, which are important factors for Internet appliances and embedded devices.

In comparison, EVM's adaptive dynamic compilation technology requires less memory, requires no disk storage for virtual memory, and only compiles the code that represents the current performance bottlenecks in the application or that accelerates critical aspects of an application's code. The remainder of the application code runs interpreted.

As the application runs, the EVM determines which code segments execute most frequently and compiles and stores them into the configured amount of code buffer memory. Once the allotted code buffers are used, the EVM may recycle the buffers to optimize performance in the given footprint.

Benchmarks conducted by Insignia customers, partners, and independent third parties running the industry-standard Embedded CaffeineMark 3.0 confirmed that the Jeode EVM executes Java applications on average six to ten times faster than interpretive VMs.

The behavior of an Internet appliance or embedded device application needs to be reliable, consistent, and robust. Unscheduled pauses in the application's execution are unacceptable in most environments, and reliability is largely determined by the "garbage collection" strategy used to manage memory.

Figure 3: Compared to batch and incremental garbage collection, the concurrent garbage collection used by EVM schedules and reduces the length of pauses and also conserves memory.

The Jeode EVM implements precise, fully concurrent garbage collection technology with memory compaction to eliminate memory fragmentation. This approach frees up all unreferenced objects and avoids memory leaks. The garbage collector runs as a pre-emptible thread, and its priority can be set by the application. Because it is implemented as a fully concurrent thread, this process adds minimal overhead to the context switch time when switching to a higher priority application thread.

The dynamic adaptive compiler also operates as a thread and is pre-empted by any higher priority threads in the system. In addition, the amount of memory used by the EVM can be bounded, and the usage of memory may adapt dynamically depending on the current needs of the application.

To enhance robustness, each of the EVM components handles failures to acquire more memory. If a memory request fails, for example, the EVM may generate an exception that can be appropriately managed rather than causing the system to crash.

Finally, each Java thread is mapped to an underlying thread in the real-time operating system (RTOS), providing improved integration with native threads and tighter synergy with the RTOS scheduler.

The platform's tools reduce the memory needed by the virtual machine to run a Java application and also manage memory to maximize performance within the constraints of the available resources. The Jeode configurator assists in specifying the parameters for a specific implementation of the EVM. Size can be configured for functionality and performance trade-offs for each specific application.

The actual ROM size required for the EVM can vary anywhere from approximately 360 KB to 4.0 MB for all class libraries with English language support to approximately 5.0 MB for all class libraries with full international language support.

The Jeode EVM can be configured and tuned to aid in the definition of a specific implementation for a particular Internet appliance or embedded device. For example, you can specify the maximum system memory, maximum heap size, maximum stack size, and several parameters associated with dynamic compilation.

Figure 4: Configuration options allow you to set parameters such as maximum heap size, system memory, and stack size using the Jeode configurator.

It can be highly instrumented to provide diagnostic and debugging insights into the EVM itself. The application's behavior can be observed as it executes relative to parameters that are selected to configure and tune the EVM and dynamic compiler. For example, you can view the amount of heap that was used during execution and watch the change in heap size as the garbage collector runs to bound the amount of heap that is actually consumed.

The platform currently supports a variety of operating systems and target processors, including Windows CE, Pocket PC, Linux, VxWorks, Windows NT, Windows NT Embedded, and ITRON operating systems as well as x86, MIPS, ARM, Hitachi SH, and PowerPC processors. Custom porting services or source code licensing is available to expedite porting to platforms required by customers.

It also has been integrated as a plug-in for the Internet Explorer browser for Windows CE, PocketPC, and Windows NT Embedded. The plug-in enables the browser to load and run Java applets.

The Jeode platform provides Java functionality for devices such as the Compaq iPAQ Home Internet Appliance and Fujitsu PC PenCentra 200 pen tablet computer.