Hard real-time Java virtual machine for Space applications

International audienceThe AERO ($UFKLWHFWXUH IRU (QKDQFHG 5HSURJUDPPDELOLW\ DQG 2SHUDELOLW\) is an ESA project with the objectives to investigate on a real-time Java virtual machine for ERC32 processor. Special attention was put on the garbage collection mechanism and deterministic execution model. The project have first investigate existing virtual machine to choose a potential candidate that will be customized, are then investigates the definition of requirements concerning a real-time interpreter in on-board systems. The second phase of the project was dedicated to the definition of software functions of the real-time Java virtual machine and to their implementation and assessment through validation tests. The resulting application is the AERO-JVM

Realtime garbage collection in the JamaicaVM 3.0

This paper provides an overview of the realtime garbage col-lector 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 col-lector 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 col-lector using explicit pacing that requires information on the application’s 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 op-timisation such as a faster write-barrier and a sweep phase that does not need to touch the objects and therefore re-duces the number of cache misses caused during sweep

Abstract Guaranteeing Non-Disruptiveness and Real-Time Deadlines in an Incremental Garbage Collector

For Garbage Collection (GC) to be a generally accepted means of memory management it is required to prove its efficiency. This paper presents a scheme that guarantees that an incremental Garbage Collector will have completed its collection cycle before the system runs out of memory. Furthermore, it is shown that the work that has to be done by the collector in one incremental step is limited by a small constant depending on the percentage of total memory used by the application program. This result then allows a suitable trade-off between memory demand and GC overhead to be found. 1

Abstract Guaranteeing Non-Disruptiveness and Real-Time Deadlines in an Incremental Garbage Collector

For Garbage Collection (GC) to be a generally accepted means of memory management it is required to prove its efficiency. This paper presents a scheme that guarantees that an incremental Garbage Collector will have completed its collection cycle before the system runs out of memory. Furthermore, it is shown that the work that has to be done by the collector in one incremental step is limited by a small constant depending on the percentage of total memory used by the application program. This result then allows a suitable trade-off between memory demand and GC overhead to be found. 1