Jalapeño is a virtual machine for Java TM servers written in the Java language. To be able to address the requirements of servers (performance and scalability in particular), Jalapeño was designed "from scratch" to be as self-sufficient as possible. Jalapeño's unique object model and memory layout allows a hardware null-pointer check as well as fast access to array elements, fields, and methods. Run-time services conventionally provided in native code are implemented primarily in Java. Java threads are multiplexed by virtual processors (implemented as operating system threads). A family of concurrent object allocators and parallel type-accurate garbage collectors is supported. Jalapeño's interoperable compilers enable quasi-preemptive thread switching and precise location of object references. Jalapeño's dynamic optimizing compiler is designed to obtain high quality code for methods that are observed to be frequently executed or computationally intensive.

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Jalapeno is a virtual machine for JavaTM servers written in Java.A running Java program involves four layers of functionality: the user code, the virtual-machine, the operating system, and the hardware.By drawing the Java / non-Java boundary below the virtual machine rather than above it, Jalapeiio reduces the boundary-crossing overhead and opens up more opportunities for optimization. To get Jalapeno started, a boot image of a working Jalapeiio virtual machine is concocted and written to a file. Later, this file can be loaded into memory and executed. Because the boot image consists entirely of Java objects, it can be concocted by a Java program that runs in any JVM. This program uses reflection to convert the boot image into Jalapeno's object format.A special MAGIC class allows unsafe casts and direct access to the hardware.Methods of this class are recognized by Jalapeno's three compilers, which ignore their bytecodes and emit special-purpose machine code. User code will not be allowed to call MAGIC methods so Java's integrity is preserved.A small non-Java program is used to start up a boot image and as an interface to the operating system. Java's programming features -object orientation, type safety, automatic memory management -greatly facilitated development of Jalapeno. However, we also discovered some of the langauge's limitations.

Discussed is a methodology for discovering operating system design jaws as an approach to learning system design techniques that may make possible greater data security. Inputloutput has been found to be involved in most of the weaknesses discovet-ed by a study team in a particular version of the system. Relative design simplicity was found to be the source of greatest protection against penetration eforts.

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