Date: Thursday 27 March 2014
Time: 08:30 - 10:00
Location / Room: Konferenz 4

Chair:
Giuseppe Lipari, ENS - Cachan, FR

Co-Chair:
Benny Akesson, CTU Prague, CZ

This session deals with scheduling and schedulability analysis of real-time systems. In particular, it presents different models of scheduling, including fixed and dynamic priority, and real-time calculus.

Time	Label	Presentation Title Authors
08:30	9.6.1	RATE-ADAPTIVE TASKS: MODEL, ANALYSIS, AND DESIGN ISSUES Speakers: Giorgio Buttazzo1, Enrico Bini2 and Darren Buttle3 1Scuola Superiore Sant'Anna, IT; 2Lund University, SE; 3ETAS-PGA/PRM-E, DE Abstract In automotive systems, some of the engine control tasks are triggered by specific crankshaft rotation angles and are designed to adapt their functionality based on the angular velocity of the engine. This paper proposes a new task model for specifying such a type of real-time activities and presents an approach for analyzing the system feasibility under deadline scheduling for different scenarios. In particular, a feasibility test is derived for tasks under steady-state conditions (constant speed), as well as in dynamic conditions (constant acceleration). A design method is also discussed to determine the most suitable switching speeds for adapting the functionality of tasks without exceeding a desired utilization. Finally, a number of research directions are highlighted to extend the current results to more complex and realistic scenarios.
09:00	9.6.2	ACCEPTANCE AND RANDOM GENERATION OF EVENT SEQUENCES UNDER REAL TIME CALCULUS CONSTRAINTS Speakers: Kajori Banerjee and Pallab Dasgupta, Indian Institute of Technology Kharagpur, IN Abstract Simulation platforms for complex networked real time systems require random input pattern generators for simulating input distributions. They also require monitors for checking whether the output of the system satisfies the desired throughput. In this paper we study the acceptance and generation problems in a setting where the constraints defining the input distributions as well as the constraints defining the expected output distributions are specified in real time calculus (RTC). We prove that event patterns satisfying a given set of RTC constraints can be described by a omega-regular language. We propose a method for constructing an automaton that can be used for online generation of random admissible event patterns. This is significant, considering the known problems of deadlock in less informed generators for streams satisfying RTC constraints
09:30	9.6.3	GENERAL AND EFFICIENT RESPONSE TIME ANALYSIS FOR EDF SCHEDULING Speakers: Nan Guan and Wang Yi, Uppsala University, SE Abstract Response Time Analysis (RTA) is one of the key problems in real-time system design. This paper proposes new RTA methods for EDF scheduling, with general system models where workload and resource availability are represented by request/demand bound functions and supply bound functions. The main idea is to derive response time upper bounds by lower-bounding the slack times. We first present a simple over-approximate RTA method, which lower bounds the slack time by measuring the "horizontal distance" between the demand bound function and the supply bound function. Then we present an exact RTA method based on the above idea but eliminating the pessimism in the first analysis. This new exact RTA method, not only allows to precisely analyze more general system models than existing EDF RTA techniques, but also significantly improves analysis efficiency. Experiments are conducted to show efficiency improvement of our new RTA technique, and tradeoffs between the analysis precision and efficiency of the two methods in this paper are discussed.
09:45	9.6.4	THE SCHEDULABILITY REGION OF TWO-LEVEL MIXED-CRITICALITY SYSTEMS BASED ON EDF-VD Speakers: Dirk Mueller and Alejandro Masrur, TU Chemnitz, DE Abstract The algorithm Earliest Deadline First with Virtual Deadlines (EDF-VD) was recently proposed to schedule mixed-criticality task sets consisting of high-criticality (HI) and low-criticality (LO) tasks. EDF-VD distinguishes between HI and LO mode. In HI mode, the HI tasks may require executing for longer than in LO mode. As a result, in LO mode, EDF-VD assigns virtual deadlines to HI tasks (i.e., it uniformly downscales deadlines of HI tasks) to account for an increase of workload in HI mode. Different schedulability conditions have been proposed in the literature; however, the schedulability region to fully characterize EDF-VD has not been investigated so far. In this paper, we review EDF-VD's schedulability criteria and determine its schedulability region to better understand and design mixed-criticality systems. Based on this result, we show that EDV-VD has a schedulability region being around 85% larger than that of the Worst-Case Reservations (WCR) approach.
10:00		End of session Coffee Break in Exhibition Area On Tuesday-Thursday the coffee and lunch breaks will be located in the Exhibition Area (Terrace Level).