Schedulability analysis for a combination of preemptive strict periodic tasks and sporadic tasks

International audienceWe consider the problem of scheduling tasks with strict periods combined with sporadic tasks. Both types of task have fixed priorities and are preemptive. For a task with a strict period, %it is necessary to prove that for any job of the task, the difference between its starting time and its release time must be identical for every job. Tasks with strict periods are typically in charge of controlling the activities of a system (sensor/actuator, feedback control, ect.). The freshness of the information they use and/or the reactivity of the system are constrained. Indeed, for control tasks, it might be important to control their jitters (the difference between the worst case and the minimum response time) to ensure the stability of the control loop. In this paper, we consider for controlled tasks, the solution satisfying property that minimizes the jitter of tasks with strict periods. For any task with strict period, (i) the start time of any job of the task must be equal to its release time and (ii) the Worst Case Response Time (WCRT) of the task must be equal to its Worst Case Execution Time (WCET). In this paper, we provide a sufficient schedulability condition for the schedulability of tasks with strict periods. We show how to define their first release times such that property \ref{property-P1} is met (based on paper \cite{rtns10}). Tasks with strict periods have the same fixed priority, the highest one. Sporadic tasks all have a lower priority than any task with a strict period. We show in this paper how to define the worst case scenario for the schedulability of sporadic tasks in the presence of tasks with strict periods. Then we propose a schedulability condition for sporadic tasks based on the worst case response time computation

Neutrinos from Stored Muons nuSTORM: Expression of Interest

The nuSTORM facility has been designed to deliver beams of electron and muon neutrinos from the decay of a stored muon beam with a central momentum of 3.8 GeV/c and a momentum spread of 10%. The facility is unique in that it will: serve the future long- and short-baseline neutrino-oscillation programmes by providing definitive measurements of electron-neutrino- and muon-neutrino-nucleus cross sections with percent-level precision; allow searches for sterile neutrinos of exquisite sensitivity to be carried out; and constitute the essential first step in the incremental development of muon accelerators as a powerful new technique for particle physics. Of the world's proton-accelerator laboratories, only CERN and FNAL have the infrastructure required to mount nuSTORM. Since no siting decision has yet been taken, the purpose of this Expression of Interest (EoI) is to request the resources required to: investigate in detail how nuSTORM could be implemented at CERN; and develop options for decisive European contributions to the nuSTORM facility and experimental programme wherever the facility is sited. The EoI defines a two-year programme culminating in the delivery of a Technical Design Report

nuSTORM - Neutrinos from STORed Muons: Proposal to the Fermilab PAC

The nuSTORM facility has been designed to deliver beams of electron neutrinos and muon neutrinos (and their anti-particles) from the decay of a stored muon beam with a central momentum of 3.8 GeV/c and a momentum acceptance of 10%. The facility is unique in that it will: 1. Allow searches for sterile neutrinos of exquisite sensitivity to be carried out; 2. Serve future long- and short-baseline neutrino-oscillation programs by providing definitive measurements of electron neutrino and muon neutrino scattering cross sections off nuclei with percent-level precision; and 3. Constitutes the crucial first step in the development of muon accelerators as a powerful new technique for particle physics. The document describes the facility in detail and demonstrates its physics capabilities. This document was submitted to the Fermilab Physics Advisory Committee in consideration for Stage I approval

First muon-neutrino disappearance study with an off-axis beam

We report a measurement of muon-neutrino disappearance in the T2K experiment. The 295-km muon-neutrino beam from Tokai to Kamioka is the first implementation of the off-axis technique in a long-baseline neutrino oscillation experiment

Job vs. portioned partitioning for the earliest deadline first semi-partitioned scheduling

International audienceIn this paper, we focus on the semi-partitioned scheduling of sporadic tasks with constrained deadlines and identical processors. We study two cases of semi-partitioning: (i) the case where the worst case execution time (WCET) of a job can be portioned, each portion being executed on a dedicated processor, according to a static pattern of migration; (ii) the case where the jobs of a task are released on a processor, 1 time out of p, where p is an integer at most equal to the number of processors, according to a round-robin migration pattern. The first approach has been investigated in the state-of-the-art by migrating a job at its local deadline, computed from the deadline of the task it belongs to. We study several local deadline assignment heuristics (fair, based on processor utilization and based on the minimum acceptable local deadline for a job on a processor). In both cases, we propose feasibility conditions for the schedulability of sporadic tasks scheduled using earliest deadline first (EDF) semi-partitioned scheduling. We show that the load function used for global scheduling to establish the feasibility of sporadic task sets exhibits interesting properties in the semi-partitioning context. We carry out simulations to study the performance of the two approaches in terms of success rate and number of migrations, for platforms composed of four and eight processors. We compare the performance of these semi-partitioned heuristics with the performance of classical partitioned scheduling algorithms and with a global scheduling heuristic which is currently considered to have good performances

Job vs. portioned partitioning for the earliest deadline first semi-partitioned scheduling

International audienceIn this paper, we focus on the semi-partitioned scheduling of sporadic tasks with constrained deadlines and identical processors. We study two cases of semi-partitioning: (i) the case where the worst case execution time (WCET) of a job can be portioned, each portion being executed on a dedicated processor, according to a static pattern of migration; (ii) the case where the jobs of a task are released on a processor, 1 time out of p, where p is an integer at most equal to the number of processors, according to a round-robin migration pattern. The first approach has been investigated in the state-of-the-art by migrating a job at its local deadline, computed from the deadline of the task it belongs to. We study several local deadline assignment heuristics (fair, based on processor utilization and based on the minimum acceptable local deadline for a job on a processor). In both cases, we propose feasibility conditions for the schedulability of sporadic tasks scheduled using earliest deadline first (EDF) semi-partitioned scheduling. We show that the load function used for global scheduling to establish the feasibility of sporadic task sets exhibits interesting properties in the semi-partitioning context. We carry out simulations to study the performance of the two approaches in terms of success rate and number of migrations, for platforms composed of four and eight processors. We compare the performance of these semi-partitioned heuristics with the performance of classical partitioned scheduling algorithms and with a global scheduling heuristic which is currently considered to have good performances

Improving the Quality of Control of Periodic Tasks Scheduled by FP with an Asynchronous Approach

info:eu-repo/semantics/publishe

Improving the Sensitivity of Deadlines with a Speci c Asynchronous Scenario for Harmonic Periodic Tasks Scheduled by FP

Proceedings of the 4th International Conference on Systems (ICONS'09), IEEE Computer Society Press, Cancun, Mexico, March 2009.info:eu-repo/semantics/publishe