1. Introduction to the CVM and the Timesys RI

2. CVM and RI CVM from Sun Microsystems TimeSys RI
A small virtual machine designed for devices with limited resources
Accepted under the Java Community Process(JCP)
Released on March, 2002
Targets platform-specific embedded Java deviced running on ARM, PowerPC, x86, etc.
TimeSys RI
Real-Time extensions to CVM
Runs on top of TimeSys Linux/RT
Offered to test applications based on RTSJ

3. TimeSys Linux/RT Real-Time supports for Linux kernel
High-resolution clocks and timers
System clock frequency level control
nanosleep() based on processor timer(cf. 10ms min in standard Linux)
POSIX Thread scheduling APIs
SCHED_FIFO and SCHED_RR
Low latency
Preemptible kernel mutex support
Priority inheritance (PTHREAD_PRIO_INHERIT)
Priority ceiling (PTHREAD_PRIO_PROTECT)
Periodic task APIs
rt_make_periodic(period, starttime) enables a process to be periodic
Other APIs support for suspend, deadline, and period control

4. CVM
The C Virtual Machine (CVM) is the basis for J2ME CDC (Connected Device Configuration) and the FP (Foundation Profile) for consumer electronics and embedded devices.
Complete Java 2 VM
Network connectivity and common Java class libraries
Small footprint
~256KB with JNI, verifier and class loading
Modular and tunable
Pluggable GC and Profiler

5. Reference Implementation
The Timesys RI is designed to implement the requirements set forth in the real-time Java specification book, and extends the CVM on:
High resolution clock and timer
Asynchronous interrupt and event handling
Real-time threading using PThreads/RT
Priority scheduling
Memory system
Immortal, Scoped, and Raw memory access

6. PThreads support in RI
Native threading by mapping Java thread to PThreads thread
arbitrary thread pre-emption at machine instruction boundaries
Signal-based thread synchronization
Round-robin / priority scheduling supported by standard PThreads

7. CVM/RI Memory The CVM memory system features the following Exactness
Small average garbage collection pause times
Full separation of VM from the memory system
Pluggable garbage collectors
CMV includes:
Generational GC
Copy collector
Mark-and-swap