Introduction to the CVM and the Timesys RI

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

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

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

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

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

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