The document discusses JamaicaVM, a virtual machine that provides real-time response capabilities for Java applications, addressing challenges like unpredictable pauses and non-determinism. It highlights features such as a multithreaded, preemptable garbage collector, deterministic runtime performance, and compliance with real-time specification for Java (RTSJ). Ultimately, JamaicaVM aims to enhance Java's reliability in embedded and critical applications while maintaining safety and reducing memory management issues.

1. Temadag om Java
JamaicaVM
Hard Realtime Response for Java Programs
Dr. Isabel Tonin
CEO, aicas
September 2013

2. 2JamaicaVM: Realtime Response for Java Applications
Java Advantages
Deep Ecosystem
Large number of developers
Diverse middleware and libraries
Many development tools
Well defined language
Minimizes errors (strong typing w/ GC)
Security and memory model
Support for parallelism & distribution
Supports dynamic code loading (modules)

3. 3JamaicaVM: Realtime Response for Java Applications
Real-Time Specification for Java
Realtime Tasking
Realtime threads
Event handling
Priority inversion
avoidance
Control Flow
Deadline Mon & Cntrl
Overrun Mon & Cntrl
ATC
Input/Output
Raw memory
POSIX events
Happenings
Memory Areas
Immortal
Scope
Physical

4. 4JamaicaVM: Realtime Response for Java Applications
Java Problems
unpredictable pauses &
delays
Java nondeterminism
Java application size
Java performance
Java RTSJ Scoped Memory
complexity
Lack of Java on Embedded
Platforms
The JamaicaVM Solution
JamaicaVM Solution
Multithreaded, fully
preemptable Garbage
Collector (RTGC)
worst case execution time
analysis (WCETA) possible with
deterministic RTGC
Smart Linker reduces
executable size by up to 90%
ahead-of-time (AOT) compiler
delivers “native” compiled
code performance
no need for ScopedMemory
support for most embedded
OSes & CPUs including GENIVI

5. 5JamaicaVM: Realtime Response for Java Applications
Realtime Java Technology
Static compiler technology with profiling
Faster code
Better time vs. space trade off
Smart linking
Only include what is necessary
Deterministic garbage collection
GC does not interrupt other (realtime) tasks
No pauses in the application

6. 6JamaicaVM: Realtime Response for Java Applications
Deterministic Garbage Collection
Saves development time
No need to release objects explicitly
Fewer memory errors
Improves safety
Reduces the danger of memory leaks
Prevents premature object deallocation
Does not interfere with realtime response

7. 7JamaicaVM: Realtime Response for Java Applications
Certifying a Garbage Collector
Not possible for all collector
Must be deterministic; no unbound steps
Must assume maximum memory use
Must consider allocation rate
Work Based Collector
No root scan and compaction (unbound)
Mark and sweep steps on fixed size blocks
Automatically tracks allocation rate

8. 8JamaicaVM: Realtime Response for Java Applications
Conventional Garbage Collection
GC can interrupt execution for long periods of time:
Problem
long, unpredictable pauses during execution

9. 9JamaicaVM: Realtime Response for Java Applications
RTSJ & Conventional Garbage Collection
No heap threads can interrupt garbage collector:
The application must be split into a realtime and a
nonrealtime part.

10. 10JamaicaVM: Realtime Response for Java Applications
Realtime Garbage Collection
Paced garbage collector
Run GC at a high priority
Runs at given interval, for given amount of time
Programmer must provide both maximum memory use
and maximum allocation rate
Slack garbage collector
Run GC at lower priority than realtime tasks
Runs when processor cycles are available
Programmer must provide both maximum memory use
and maximum allocation rate

11. 11JamaicaVM: Realtime Response for Java Applications
Realtime Garbage Collection
Work based garbage collector
No GC thread
GC borrows application thread
Need only determine maximum memory use
No read barriers needed
Low latency

12. 12JamaicaVM: Realtime Response for Java Applications
Work-Based Garbage Collector
All Java Threads are realtime threads
GC work is performed at allocation time
GC work must be sufficient to recycle enough memory
before free memory is exhausted
Execution time of all allocations must be bound

13. 13JamaicaVM: Realtime Response for Java Applications
JamaicaVM Builder Architecture
Default
Code Generator
Machine Code
Optimization
SSA Converter
Byte Code
Reader
Java Byte
Code
Intermediate
Code
SSA Blocks
Machine
Code
Object Code
Writer
SSA IC
Optimization
Machine Code
Generator
Machine Code
Generation Rules
SSA IC
Optimization Rules
Object Code
(ELF/PECOFF)
Machine Code
Optimization Rules
Processor
Definition
C Code
Generator
C Compilation
C Code

14. 14JamaicaVM: Realtime Response for Java Applications
aicas Drives Standards Forward
Java Community Process
JSR 282: update Real-Time Specification for Java
JSR 302: Safety Critical Java
JSR 50: Distributed Realtime Java
SC-205/WG-71 Plenary
Update software standards for civil aviation:
DO-178, -248, -278, -330, -331, -332, and -333
Active in SG-5: Object Oriented Technology
Java Modeling Language (JML)

15. 15JamaicaVM: Realtime Response for Java Applications
Major RTSJ Improvements
Raw Memory
Typed device access
Factory based
ActiveEvents
Unify API for Timer,
Happening, & Signal
Happening object
ISR Support
Stateful Events &
Handlers
Object & long
POSIX Realtime Signal
CPU Affinity
New Scope types
PinnableMemory
StackedMemory

16. 16JamaicaVM: Realtime Response for Java Applications
Applications

17. 17JamaicaVM: Realtime Response for Java Applications
JamaicaVM vs. Oracle’s JDK
JamaicaVM
Realtime GC
no GC pauses
Supports realtime
priorities w/ OS map
RTSJ APIs
RealtimeThread,
AsyncEvent, etc.
Static compilation
Flexible license
Oracle’s JDK
Conventional GC
GC causes pauses
Priorities ill defined
w/o mapping to OS
No RTSJ support, just
standard classes
JIT Only
One for all license
(not free)

18. 18JamaicaVM: Realtime Response for Java Applications
Conclusion
State-of-the-art Java technology
Realtime garbage collection
Compilation and linking technology
Complete RTSJ implementation
multicore support
Market proven products
Dedicated to standards
Tools to ensure your system works correctly