Exploiting unused periodic time for aperiodic service using the extended priority exchange algorithm

Sprunt, Brinkley; Lehoczky, John P.; Li, Sha

doi:10.1109/real.1988.51120

Cited by 80 publications

(30 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Not all the bandwidth preserving algorithms can reclaim gain time at any high priority. The extended priority exchange algorithm [96], slack stealing algorithm [62] and dual-priority scheduling algorithm [36] are examples of those algorithms that can reclaim gain time at high priorities. A straightforward approach to identifying gain time is to compare a task's real execution time with its WCET when the task completes.…”

Section: Flexible Real-time Schedulingmentioning

confidence: 99%

Garbage Collection for Flexible Hard Real-Time Systems

Chang

Wellings

2010

IEEE Trans. Comput.

View full text Add to dashboard Cite

Garbage collection is key to improving the productivity and code quality in virtually every computing system with dynamic memory requirements. It dramatically reduces the software complexity and consequently allows the programmers to concentrate on the real problems rather than struggling with memory management issues, which finally results in higher productivity. The code quality is also improved because the two most common memory related errors -dangling pointers and memory leaks -can be prevented (assuming that the garbage collectors are implemented correctly and the user programs are not malicious).However, real-time systems, particularly those with hard real-time requirements, always choose not to use garbage collection (or even dynamic memory) in order to avoid the unpredictable executions of garbage collectors as well as the chances of being blocked due to the lack of free memory. Much effort has been expended trying to build predictable garbage collectors which can provide both temporal and spatial guarantees. Unfortunately, most existing work leads to systems that cannot easily achieve a balance between temporal and spatial performance, although their worst-case behaviours in both dimensions can be predicted. Moreover, the real-time systems targeted by the existing real-time garbage collectors are not the state-ofthe-art ones. The scheduling of those garbage collectors has not been integrated into the modern real-time scheduling frameworks, which makes the benefits provided by those systems very difficult to obtain. This thesis argues that the aforementioned issues should be tackled by introducing new design criteria for real-time garbage collectors. The existing criteria are not enough to reflect the unique requirements of real-time systems. A new performance indicator is proposed to describe the capability of a real-time garbage collector to achieve better balance between temporal and spatial performance. Moreover, it is argued that new real-time garbage collectors should be integrated with the real-time task model and more advanced scheduling techniques should be adopted as well.A hybrid garbage collection algorithm, which combines both reference counting and mark-sweep, is designed according to the new design criteria. On the one hand, the reference counting component helps reduce the overall memory requirements. On the other hand, the mark-sweep component periodically identifies cyclic garbage, which cannot be found by the reference counting component. Both parts of the collector are executed by segregated tasks, which are released periodically as the hard real-time user tasks. In order to improve the performance of soft-or non-realtime tasks in our system while still guaranteeing the hard real-time requirements, the dual-priority scheduling algorithm is used for all the tasks including the GC tasks. A multi-heap approach is also proposed to bound the impacts of the softor non-real-time tasks on the overall memory usage as well as the executions of the GC tasks. More importantly, static ana...

show abstract

Section: Flexible Real-time Schedulingmentioning

confidence: 99%

Garbage Collection for Flexible Hard Real-Time Systems

Chang

Wellings

2010

IEEE Trans. Comput.

View full text Add to dashboard Cite

show abstract

“…When the server's period commences, the server runs if there is any outstanding non-periodic requests. If no requests exist, the priority exchange algorithm 43,69 allows the high priority server to exchange its priority with a lower priority periodic process. In this way, the server's priority decreases but time reserved for non-periodic processes is maintained.…”

Section: Priority Exchangementioning

confidence: 99%

Real-Time System Scheduling

Audsley

Burns

Davis

et al. 1995

Predictably Dependable Computing Systems

View full text Add to dashboard Cite

Recent results in the application of scheduling theory to dependable real-time systems are reviewed. The review takes the form of an analysis of the problems presented by different application requirements and characteristics. Issues covered include uniprocessor and multiprocessor systems, periodic and aperiodic processes, static and dynamic algorithms, transient overloads and resource usage. Protocols that bound and reduce blocking are discussed. A review of specific real-time kernels is also included.

show abstract

“…The first algorithm using this concept to handle aperiodic tasks was known as the priority * exchange algorithm [8,23]. This algorithm was shown to have very good theoretical performance and to be fully compatible with the rate monotonic scheduling algorithm.…”

Section: Cmu/sei-91-tr-6mentioning

confidence: 99%