Fiji VM Safety Critical Java

Transcription

1 Fiji VM Safety Critical Java Filip Pizlo, President Fiji Systems Inc.

2 Introduction Java is a modern, portable programming language with wide-spread adoption. Goal: streamlining debugging and certification. Safety Critical Java (SCJ) brings the benefits of Java to the safety-critical space. The Fiji VM is a high-performance, low-footprint Safety Critical Java implementation.

3 Java and Safety Top defects in existing embedded code: * Buffer overflow and underflow Null object dereference Uninitialized variable Inappropriate cast Division by zero Memory leaks impossible in Java checked in Java impossible in Java checked in Java checked in Java GC Source: Diagnosing Medical Device Software Defects Medical DeviceLink, May 2009

4 Java s safety also gives you fine-grained space partitioning and isolation for free. Standard language taught in universities around the world. Java is known to scale to 800+ cores; rich library support for parallel/concurrent programming. Concurrency in Java is fast. Java locks are at least 50% faster than POSIX locks on Linux. Rich tool support (IDEs, bug finders, verification tools, modeling tools, etc.) Java supports safe dynamic loading.

5 Summary of Java s benefits A subset of program errors go away. For the remaining program errors: Java programs are more analyzable, making model-checking easier. Java programs are more testable, thanks to extensive tool support for unit testing. Java programs are more readable, making code audits simpler. Java brings a plethora of modern language features that make software engineering more cost-effective.

6 Java for Real Time NIST prepared a set of requirements for RT Java JSR-001, first draft specification Real Time Specification for Java (RTSJ) accepted SUN and IBM release RTSJ implementations JSR-302 Safety Critical Java started development of Fiji VM SCJ begins.

7 Fiji VM High-performance Real Time Java

8 Fiji VM Compiles Java to fast machine code no interpretation! competitive with C code! Small footprint (~100KB) Strong real-time support Real Time Garbage Collection and scoped memory Can write device drivers in Java Multi-core ready Portable (x86, PPC, SPARC, ARM, others) Runs on RTEMS, Linux, others

9 Fiji VM is a compiler Java Source Code javac fivmc machine code Fiji VM uses Java byte code as input (versions 1.0 through 7 supported) Fiji VM produces executables. Your code is never interpreted. Result: small footprint, fast and predictable execution.

10 Fiji VM real-time support Striving for Safety-critical Java (SCJ) compliance, targeting DO-178B and DO-178C level A certification. Every operation has predictable timing. Memory usage is predictable. both garbage collection and SCJ scoped memory

11 Fiji VM Garbage Collection Garbage collection allows safe, fragmentation-free dynamic memory allocation. Garbage collector runs as a separate thread. The scheduling of this thread can be programmatically controlled. We provide WCET and schedulability formulas that describe how much CPU time this thread should get. Application threads see no interference from the GC.

12 Concurrency Support Demonstrated scalability to 8 cores. High-performance locking support: Priority Inheritance, Inline Locks, and Biased Locks Support for non-blocking synchronization.

13 Customizable GC Fragmentation allowed but bounded (like malloc/free) Conventional Java MMTk GenImmix no fragmentation no pauses Fiji CMR Fiji Schism/cmr Predictability/Certifiability Throughput

14 Customizable footprint More Java features, excellent for mission-critical systems 2 MB Hard Safety Critical profile 500 KB GNU Classpath 100 KB FijiCore SCJ FijiMicro SCJ Standard Java profile More Compact More Features

15 Execution time vs. Competition 83% faster than leading competitor.

16 Predictability Standard JVM Fiji VM >100ms pauses! no pauses! completely predictable execution! *CDx benchmark HARD configuration.

17 Correlation: C vs. Java C Iteration Execution Time Java Iteration Execution Time

18 Against C code on RTEMS/LEON3 Java s worst-case is 10% worse than C s. GC has zero effect on predictability.

19 Integration Rapita JML Fiji VM Eclipse IDE

20 Deeply Embeddable Fiji VM allows unmodified Java programs to boot from bare hardware. Can write kernel drivers in Java. Currently works on POSIX, RTEMS. Ports to Linux kernel, vxworks, and Integrity in progress. vxworks: scheduled for mid-2010 Easy to port to new OS s

21 Summary Safety Critical Java enables a more cost-effective development process for safety-critical systems. Fiji VM allows Java code to run quickly and predictably. With Fiji VM, Java can be used anywhere that C or C++ are used, saving development costs and time.

22 Fiji VM Code Statistics Size of runtime: 20,000 lines of C code 10,000 lines of Java code this includes code for all configurations. Size of compiler: 4,000 lines of Ruby code 50,000 lines of Java code