Most recurrent real-time applications can be modeled as a set of sequential code segments (or blocks) that must be (repeatedly) executed in a specific order. This paper provides a schedulability analysis for such systems modeled as a set of parallel DAG tasks executed under any limited-preemptive global job-level fixed priority scheduling policy. More precisely, we derive response-time bounds for a set of jobs subject to precedence constraints, release jitter, and execution-time uncertainty, which enables support for a wide variety of parallel, limited-preemptive execution models (e.g., periodic DAG tasks, transactional tasks, generalized multi-frame tasks, etc.). Our analysis explores the space of all possible schedules using a powerful new state abstraction and state-pruning technique. An empirical evaluation shows the analysis to identify between 10 to 90 percentage points more schedulable task sets than the state-of-the-art schedulability test for limited-preemptive sporadic DAG tasks. It scales to systems of up to 64 cores with 20 DAG tasks. Moreover, while our analysis is almost as accurate as the state-of-the-art exact schedulability test based on model checking (for sequential non-preemptive tasks), it is three orders of magnitude faster and hence capable of analyzing task sets with more than 60 tasks on 8 cores in a few seconds.
@InProceedings{nasri_et_al:LIPIcs.ECRTS.2019.21, author = {Nasri, Mitra and Nelissen, Geoffrey and Brandenburg, Bj\"{o}rn B.}, title = {{Response-Time Analysis of Limited-Preemptive Parallel DAG Tasks Under Global Scheduling}}, booktitle = {31st Euromicro Conference on Real-Time Systems (ECRTS 2019)}, pages = {21:1--21:23}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-110-8}, ISSN = {1868-8969}, year = {2019}, volume = {133}, editor = {Quinton, Sophie}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2019.21}, URN = {urn:nbn:de:0030-drops-107587}, doi = {10.4230/LIPIcs.ECRTS.2019.21}, annote = {Keywords: parallel DAG tasks, global multiprocessor scheduling, schedulability analysis, non-preemptive jobs, precedence constraints, worst-case response time, OpenMP} }
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