In computing systems, a job may suspend itself, due to the interactions with external I/O devices or accelerators, multicore systems with shared resources, suspension-aware multiprocessor synchronization protocols, etc. For real-time embedded systems, self-suspension behavior negatively impact the schedulability of real-time tasks and typically cause substantial performance/schedulability degradation.
Fig: Two tasks τ1 (higher priority, period 5, relative deadline 5, computation time 3) and τ2 (lower priority, period 7, relative deadline 7, computation time 2) meet their deadlines in (a). Conventional schedulability analysis predicts maximum response times of 3 and 5 respectively. In (b), task τ1 suspends itself, with the result that task τ2 misses its deadline at time 14. (Source: Many suspensions many problems by Chen et al. in RTSJ 2019)
Even though some seemingly positive results have been reported for tackling self-suspending task systems in the past, the recent investigation by Prof. Dr. Jian-Jia Chen and his colleagues indicates that a significant portion of the literature (and also the majority of these results) before 2013 has been seriously flawed. Since most results before 2013 were in fact flawed (or with incomplete proofs), the investigation of self-suspending task models in real-time embedded systems has been restarted since 2015.
This project intends to investigate robust and solid fundamental algorithms and analyses to carefully mitigate (via safe and sound execution/suspension
enforcements) and analyze (via tight schedulability tests) the impact of self-suspending behavior in modern real-time embedded systems. The targeting systems are safety-critical systems with real-time requirements. Since the self-suspending behavior can introduce a high degree of complexity, new scheduling strategies or revisions of existing scheduling strategies are required. This project intends to provide fundamental breakthrough in the scheduling theory and the corresponding schedulability analysis to flexibly accommodate the self-suspension behavior without introducing much pessimism when considering the worst-case timing behavior.
With the scheduling strategies and schedulability tests provided in this project, we aim to offer tools for real-time system designers so that further optimizations by considering the perspectives of controllers, communications, and computation are possible.
|Duration:||Nov. 2019 - Oct. 2022 (3 years)|
|Hired:||M.Sc. Mario Günzel|
- Suspension-Aware Earliest-Deadline-First Scheduling Analysis.
Mario Günzel, Georg Brüggen and Jian-Jia Chen.
IEEE Trans. Comput. Aided Des. Integr. Circuits Syst. 39(11): 4205-4216
(presented in ACM Conference on Embedded Software, EMSOFT)
- Correspondence Article: Counterexample for suspension-aware schedulability analysis of EDF scheduling.
Mario Günzel and Jian-Jia Chen.
Real Time Systems Journal, 56(4): 490-493 (2020)
- On Schedulability Analysis of EDF Scheduling by Considering Suspension as Blocking.
Mario Günzel and Jian-Jia Chen.
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Location & approach
The campus of TU Dortmund University is located close to interstate junction Dortmund West, where the Sauerlandlinie A 45 (Frankfurt-Dortmund) crosses the Ruhrschnellweg B 1 / A 40. The best interstate exit to take from A 45 is "Dortmund-Eichlinghofen" (closer to Campus Süd), and from B 1 / A 40 "Dortmund-Dorstfeld" (closer to Campus Nord). Signs for the university are located at both exits. Also, there is a new exit before you pass over the B 1-bridge leading into Dortmund.
To get from Campus Nord to Campus Süd by car, there is the connection via Vogelpothsweg/Baroper Straße. We recommend you leave your car on one of the parking lots at Campus Nord and use the H-Bahn (suspended monorail system), which conveniently connects the two campuses.
TU Dortmund University has its own train station ("Dortmund Universität"). From there, suburban trains (S-Bahn) leave for Dortmund main station ("Dortmund Hauptbahnhof") and Düsseldorf main station via the "Düsseldorf Airport Train Station" (take S-Bahn number 1, which leaves every 20 or 30 minutes). The university is easily reached from Bochum, Essen, Mülheim an der Ruhr and Duisburg.
You can also take the bus or subway train from Dortmund city to the university: From Dortmund main station, you can take any train bound for the Station "Stadtgarten", usually lines U41, U45, U 47 and U49. At "Stadtgarten" you switch trains and get on line U42 towards "Hombruch". Look out for the Station "An der Palmweide". From the bus stop just across the road, busses bound for TU Dortmund University leave every ten minutes (445, 447 and 462). Another option is to take the subway routes U41, U45, U47 and U49 from Dortmund main station to the stop "Dortmund Kampstraße". From there, take U43 or U44 to the stop "Dortmund Wittener Straße". Switch to bus line 447 and get off at "Dortmund Universität S".
The AirportExpress is a fast and convenient means of transport from Dortmund Airport (DTM) to Dortmund Central Station, taking you there in little more than 20 minutes. From Dortmund Central Station, you can continue to the university campus by interurban railway (S-Bahn). A larger range of international flight connections is offered at Düsseldorf Airport (DUS), which is about 60 kilometres away and can be directly reached by S-Bahn from the university station.
The H-Bahn is one of the hallmarks of TU Dortmund University. There are two stations on Campus Nord. One ("Dortmund Universität S") is directly located at the suburban train stop, which connects the university directly with the city of Dortmund and the rest of the Ruhr Area. Also from this station, there are connections to the "Technologiepark" and (via Campus Süd) Eichlinghofen. The other station is located at the dining hall at Campus Nord and offers a direct connection to Campus Süd every five minutes.