Scalable Online Feasibility Tests for Admission Control in a Java Real-Time System

In the Komodo project a real-time Java system based on a multithreaded Java microcontroller has been developed. A main scheduling policy realized by hardware in the microcontroller core is a new scheme called Guaranteed Percentage (GP) scheduling. This scheme assigns each thread a guaranteed percentage of the processor power thus providing a strict isolation of the threads on the processor. To prevent processor overload in the dynamic Java environment, fast online feasibility tests are necessary before a new thread is allowed to enter the microcontroller. Starting with the well known Processor Demand Analysis, a new test based on the periodic transformation of the processor workload is developed. This is a sufficient (but not necessary) scalable test, where the number of feasible thread sets found can be controlled by the costs. Furthermore, this test can be stopped, if a given cost or time limit is reached. We additionally propose a modified version of this test, which further reduces the costs and allows an online hardware feasibility test with a polynomial complexity of O(n(n + 1)/2). An evaluation shows, that the tests proposed here are able to find more than 90% of the feasible thread sets and all non-feasible thread sets with costs suitable for online testing. U. Brinkschulte was born February 16, 1959 in Mannheim, Germany. He received his M.S. (Dipl. Ing.) in electrical engineering in 1982 and his Ph.D. (Dr. rer. nat.) degree in 1990 from the University of Karlsruhe, Germany. After receiving his Ph.D., he worked as managing director with the ITV GmbH, Heiligenberg, Germany and as research and development manager with the GAI GmbH, Friedrichshafen, Germany. In 1994 he became professor of computer science at the University of Applied Science in Heidelberg. Since 1995 he is professor at the University of Karlsruhe, institute for process control, automation and robotics. His general research area are distributed real-time systems. His current interests are in self-organization of these systems and organic computing. Prof. Dr. Brinkschulte is author and coauthor of several scientific books, journal articles and conference papers.     

The influence of CO and CO2laser performance

Impurities are necessary to achieve considerable CW laser action in CO2since in pure CO2the disintegration of the lower laser level is too slow to maintain a substantial population inversion. The dissociation product CO, provided by the discharge itself if initially pure CO2is used in a sealed system, enhances the gain mainly because of its effectiveness in accelerating the relaxation of the first level of the bending mode to which the lower laser level relaxes. The characteristic time for energy exchange between these two levels is20 pm 5 mus at 1 torr, 400°K. Experiments in He-CO2mixtures support the assumption that the main influence of CO is to accelerate the decomposition of the lower laser level.     

Real-Time Garbage Collection for a Multithreaded Java Microcontroller

We envision the upcoming of microcontrollers and systems-on-chip that are based on multithreaded processor kernels due to the fast context switching ability of hardware multithreading. Moreover we envision an extensive market for Java-based applications in embedded real-time systems. This paper introduces two new garbage collection algorithms that are dedicated to real-time garbage collection on a multithreaded Java microcontroller. Our garbage collector runs in a thread slot in parallel to real-time applications. We show that our algorithms require only about 5–10% of the processor time for an effective garbage collection concerning our real-time benchmarks.