Existing real-time research focuses on how to formulate. model and enforce timeliness guarantees for task sets whose correctness has a temporal aspect. However; the resulting systems often exhibit poor resource utilization due to the resource scheduler reserving more resources than required in order to ensure that admitted schedules can be satisfied under worst case conditions. Weakening the guarantees leads to the known concepts of firm and soft real-time tasks, butt we think the paradigm needs to be shifted further,: reifying efficient utilization. With Quality-Assuring Scheduling (QAS) we presented such an algorithm. However: its practical applicability is restricted to uniform and harmonic periods, due to its complexity for arbitrary periods. To overcome this limitation, we introduce Quality-Rate-Monotonic Scheduling (QRMS), which, although slightly more pessimistic, is less complex compared to QAS. Thee admission control is again based on a probabilistic model to ensure that a requested fraction of jobs is successfully executed. Thus the amount of missed deadlines can be externally controlled, even in sustained overload situations.

Open real-time systems provide for co-hosting hard-, soft- and non-real-time applications. Microkernel-based designs in addition allow for these applications to be mutually protected. Thus, trusted servers can coexist next to untrusted applications. These systems place a heavy burden on the performance of the message-passing mechanism, especially when based on microkernel-like inter-process communication. In this paper we introduce capacity-reserve donation (in short Credo), a mechanism for the fast interaction of interdependent components, which is applicable to common real-time resource-access models. We implemented Credo by extending L4's message-passing mechanism to provide proper resource accounting and time-donation control, thereby preserving desired real-time properties. We were able to achieve priority inheritance and stack-based priority-ceiling resource sharing with virtually no overhead added to L4's message-passing implementation. By providing a. mechanism that does not impose performance penalties, while still guaranteeing correct real-time behaviour, Credo allows for the usage of microkernels in general-purpose but also in specialized systems.

article The performance of μ-kernel-based systems Share on Authors: Hermann Härtig Dresden University of Technology, Department of Computer Science, D-01062 Dresden, Germany Dresden University of Technology, Department of Computer Science, D-01062 Dresden, GermanyView Profile , Michael Hohmuth Dresden University of Technology, Department of Computer Science, D-01062 Dresden, Germany Dresden University of Technology, Department of Computer Science, D-01062 Dresden, GermanyView Profile , Jochen Liedtke IBM T. J. Watson Research Center, 30 Saw Mill River Road, Hawthorne, NY IBM T. J. Watson Research Center, 30 Saw Mill River Road, Hawthorne, NYView Profile , Sebastian Schönberg Dresden University of Technology, Department of Computer Science, D-01062 Dresden, Germany Dresden University of Technology, Department of Computer Science, D-01062 Dresden, GermanyView Profile , Jean Wolter Dresden University of Technology, Department of Computer Science, D-01062 Dresden, Germany Dresden University of Technology, Department of Computer Science, D-01062 Dresden, GermanyView Profile Authors Info & Claims ACM SIGOPS Operating Systems ReviewVolume 31Issue 5Dec. 1997 pp 66–77https://doi.org/10.1145/269005.266660Online:01 October 1997Publication History 177citation6,894DownloadsMetricsTotal Citations177Total Downloads6,894Last 12 Months272Last 6 weeks40 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access