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Dive into the research topics where Fridtjof Siebert is active.

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Featured researches published by Fridtjof Siebert.


java technologies for real-time and embedded systems | 2007

Realtime garbage collection in the JamaicaVM 3.0

Fridtjof Siebert

This paper provides an overview of the realtime garbage collector used by the RTSJ Java Virtual Machine JamaicaVM. A particular emphasis will be made on the improvements made in with release 3.0 JamaicaVM. The JamaicaVM garbage collector is incremental to an extreme extent: single incremental steps of the garbage collector correspond to scanning only 32 bytes of memory and have a worst-case execution time in the order of one μsec. The JamaicaVM garbage collector uses automatic pacing, making the system easier to configure than a garbage collector using explicit pacing that requires information on the applications allocation rate. The recent improvements of the garbage collector that will be present in this paper include support for automatic heap expansion; reduction of the memory overhead for garbage collector internal structures; and significant performance optimisation such as a faster write-barrier and a sweep phase that does not need to touch the objects and therefore reduces the number of cache misses caused during sweep.


international symposium on memory management | 2008

Limits of parallel marking garbage collection

Fridtjof Siebert

More and more, parallel multicore systems will be used even in low-end devices such as embedded controllers that require realtime guarantees. When garbage collection is used in these systems, parallel or concurrent garbage collection brings important performance advantages. In the context of realtime systems, it has to be shown that a parallel garbage collector implementation not only performs well in most cases, but guarantees on its performance in the worst case are required. This paper analyses the difficulties a parallel mark-and-sweep garbage collector faces during a parallel mark phase. The performance of such a garbage collector degrades when only some of the available processors can perform scanning work in the mark phase. Whenever the grey set contains fewer elements than the number of available processors, some processors may be stalled waiting for new objects to be added to the grey set. This paper gives an upper bound for the number of stalls that may occur as a function of simple properties of the memory graph. This upper bound is then determined for the Java applications that are part of the SPECjvm98 benchmark suite and the theoretical worst-case scalability of a parallel mark phase is analysed. The presented approach is then applied to a Java virtual machine that has uniform mark steps, which at first results in poor worst-case scalability. A small change in the implementation is then proposed and analysed to achieve good scalability even in the worst case.


international symposium on object/component/service-oriented real-time distributed computing | 2004

The impact of realtime garbage collection on realtime Java programming

Fridtjof Siebert

Extensions like the real-time specification for Java (RTSJ) enable the use of Java in more and more time-critical application domains. The RTSJ enables the development of realtime code in Java even though a classical garbage collector causes unpredictable pauses to non-realtime code. We give an overview of how a modern realtime garbage collectors operates. It presents the impact the presence of such a realtime garbage collector has on the development of complex applications that need to perform time-critical and nontime-critical tasks. The use of realtime garbage collection technology simplifies the application development even in systems that do not use dynamic memory allocation within realtime code


java technologies for real-time and embedded systems | 2006

Provably correct loops bounds for realtime Java programs

James J. Hunt; Fridtjof Siebert; Peter H. Schmitt; Isabel Tonin

Determining concrete bounds for loops is one of the more vexing problems of resource analysis of realtime programs. Current mechanisms are limited in scope and require considerable user input that can not be verified. The authors present a methodology for providing more general loop bounds where the correctness can be demonstrated with formal techniques. The methodology combines data flow analysis and deductive formal verification to attain this goal.


java technologies for real-time and embedded systems | 2006

Proving the absence of RTSJ related runtime errors through data flow analysis

Fridtjof Siebert

The Real-Time Specification for Java (RTSJ) introduces region based memory management to avoid the need for garbage collection. This region based memory management, however, introduces new possible runtime errors. Ensuring that an RTSJ application executes correctly requires proving that no memory related runtime excpetions can occur.The use of program-wide pointer analysis for proving the absence of runtime error conditions such as null pointer uses or illegal casts is still not widespread. Current uses of program-wide pointer analysis focus on extracting information for optimisations in compilers. In this case, imprecise analysis results only in less agressive optimisation, which is often tolerable.This papers presents the application of a program-wide data flow analysis to prove the absence of memory related runtime errors such as those introduced by the RTSJ.


java technologies for real-time and embedded systems | 2008

Using global data flow analysis on bytecode to aid worst case execution time analysis for real-time Java programs

James J. Hunt; Isabel Tonin; Fridtjof Siebert

Though real-time Java offers significant advantages over other programming languages for safe programming, the analysis of worst case execution of real-time Java programs is considerably more difficult. The extra complexity can be addressed using a minimal set of parameterized annotations and data flow analysis to provide a standard worst case execution time analysis tool with the additional information necessary to determine the worst case execution time analysis of real-time Java programms. This methodology has the advantage over existing methods in that it is equally applicable to general purpose library code as to application specific implementation code.


international symposium on object/component/service-oriented real-time distributed computing | 2009

JEOPARD -- Java Environment for Parallel Real-Time Development

Fridtjof Siebert

Multicore systems have become standard for desktop computers today. Current operating systems and software development tools provide straightforward means to use the additional computing power. However, a more fundamental change in the design and development of software is required to fully exploit the power of multicore systems. Furthermore, the fast growing market of embedded systems is currently largely unaffected by the introduction of multicore systems. This will change quickly in the future, which will mean that there will be a demand on ef?cient development of reliable embedded software that can give real-time guarantees and exploit the available power on multicore systems.The JEOPARD project addresses this demand by developing Java software tools to exploit multicore power while ensuring correctness and predictable timing. This paper gives an overview of the JEOPARD project and focuses on key technical issues such as real-time scheduling and real-time garbage collection on multi-core systems.


Archive | 2012

Parallel Real-Time Garbage Collection

Fridtjof Siebert

With the current developments in CPU implementations, it becomes obvious that ever more parallel multicore systems will be used even in embedded controllers that require real-time guarantees. When garbage collection is used in these systems, parallel and concurrent garbage collection brings important performance advantages in the average case. In a real-time system, however, guarantees on the GC’s performance in the worst case are required. This chapter explains the basic concepts for parallel real-time garbage collectors, the major real-time Java virtual machine implementations and their approach to parallel real-time memory management. Two implementations, Metronome-TS and JamaicaVM will be presented in more detail since these two represent two typical instances of the time-based and work-based approaches of running the garbage collector. A discussion at the end of this chapter will compare the fundamental differences in the presented approaches. A final section on related work puts the presented implementations into a wider context on current garbage collection research.


Archive | 2011

Method for implementation of memory management

Fridtjof Siebert


Archive | 2001

Method of dynamically allocating a memory

Fridtjof Siebert

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Peter H. Schmitt

Karlsruhe Institute of Technology

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