CISS Workshop on Java in Embedded Systems Realtime Java and the - PowerPoint PPT Presentation

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 46

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 47

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 48

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 49

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 50

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 51

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 52

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 53

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 54

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 55

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 56

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 57

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 58

CISS Workshop on Java in Embedded Systems Classic Garbage Collection Root Scanning Mark Sweep Compact 59

CISS Workshop on Java in Embedded Systems RTSJ with Classic Garbage Collection No heap threads can interrupt garbage collector: The application must be split into a realtime and a non-realtime part. 60

The JamaicaVM Solution Realtime Garbage Collection All Java-Threads must be 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 61

The JamaicaVM Solution Realtime Garbage Collection Root Scan Mark Sweep Compact 62

The JamaicaVM Solution Realtime Garbage Collection Root Scan Mark Sweep Compact 63

The JamaicaVM Solution Realtime Garbage Collection Root Scan Mark Sweep Compact 64

The JamaicaVM Solution Realtime Garbage Collection Root set held in heap instead of scanned Mark Sweep Compact 65

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep Compact 66

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep Compact Break objects into fixed sized blocks 67

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep Fixed sized blocks obviate compaction 68

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 69

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 70

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 71

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 72

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 73

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 74

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 75

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 76

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 77

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 78

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 79

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 80

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 81

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 82

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 83

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 84

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 85

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 86

The JamaicaVM Solution Realtime Garbage Collection Mark Sweep 87

The JamaicaVM Solution RTSJ & Realtime Garbage Collection ● The RTSJ provides necessary features for realtime programming ● Memory area restrictions can be relaxed – Can use RealtimeThread instead of NoHeapRealtimeThread – Heap allocation possible in realtime code – Synchronization possible with non realtime tasks without GC interference – GC does not interrupt thread execution 88

Safety Critical Java Safety Critical Java (JSR 302) ● Java optimized for safety critical application, e.g. DO-178B levels A and B ● Based on a subset of the RTSJ ● Uses ScopedMemory for managing deallocation instead of garbage collection ● Uses extended typing through annotations to support static analysis ● Minimum set of supported classes 89

CISS Workshop on Java in Embedded Systems Advantage of Java over C and C++ ● Clean syntax and semantics w/o preprocessor ➔ wide ranging and better tool support ● Better support for separating of subtyping and reuse via limited inheritance and interfaces ● No explicit pointer manipulation ● Pointer safe deallocation ● Single dispatch style ● Strong, extendible type system ● With RTSJ, well defined tasking model 90

The JamaicaVM Solution Tools Support ● Eclipse ● Data Flow Analysis – Refactoring – Null pointer exceptions – Remote debugging – Type caste ● Java Modeling exceptions Language – Improper – Design by contract synchronization – Runtime assertion – Array store exceptions checking – Scope and – Formal verification assignment errors 91

The JamaicaVM Solution The JamaicaVM Toolset Overview 92

The JamaicaVM Solution Build Process class class class object JVM files class files class files file library files files stand-alone settings Builder application profiling data 93

The JamaicaVM Solution Debugging and Monitoring in Java JamaicaVM Application Eclipse Standard Classes JVMTI JVM Agent Debugging Client JVMTI JDWP Host Target 94

The JamaicaVM Solution Data Flow Analysis > jamaica -dfa test NEEDEDSYNCS : 29 ( 29 locations out of 78) DEADLOCKS : 101 ( 9 locations out of 79) SCOPE CYCLES : 0 ( 0 locations out of 0) ILLEGAL ASSIGNMENTS : 0 ( 0 locations out of 764) CLASSCAST EXCEPTIONS : 128 ( 17 locations out of 90) ARRAY STORE EXCEPTIONS : 3 ( 1 locations out of 310) NULL POINTER EXCEPTIONS: 503 (139 locations out of 11041) + test.dfa_results.summary + test.dfa_results # of Source Code Positions with this problem 95

The JamaicaVM Solution Detecting Runtime Errors ... if (device instanceof MyDevice) { MySensor s = (MySensor) device.sensor; int value = s.reading(); ... } ... 96

The JamaicaVM Solution Detecting Runtime Errors ... if (device instanceof MyDevice) NullPointerException { MySensor s = (MySensor) device.sensor; int value = s.reading(); ... } ... 97

The JamaicaVM Solution Detecting Runtime Errors ... if (device instanceof MyDevice) NullPointerException { MySensor s = (MySensor) device.sensor; ClassCastException int value = s.reading(); ... } ... 98

The JamaicaVM Solution Detecting Runtime Errors ... if (device instanceof MyDevice) NullPointerException { MySensor s = (MySensor) device.sensor; ClassCastException int value = s.reading(); NullPointerException ... } ... 99

CISS Workshop on Java in Embedded Systems Detecting Runtime Errors device != null ... if (device instanceof MyDevice) NullPointerException { MySensor s = (MySensor) device.sensor; ClassCastException int value = s.reading(); NullPointerException ... } ... 100