May 20 - José Marinho, ISEP, Portugal - On Preemption Delay and WCET handling on Reservation frameworks¶

Talk abstract: The demand for time predictability on real-time systems has been addressed, in practice, by overallocation of resources to overcome the non-determinism present in code execution. With the evolution of microprocessor architecture technology, this scenario tends to move in the direction of having even more waste due to the inefficient usage of several architectural constructs geared towards the minimisation of average case execution times. This talk will cover the problem of efficient usage of caches in a multi-task preemptive system. Due to the ever increasing processor memory gap, the amount of knowledge on the cache state available on the system, has a strong impact on the resource allocation decisions taken. Some cache related preemption delay algorithms will be presented along with a method for managing CRPD on run-time.

Speaker Bio.: José Marinho is an Electrical Engineer from the University of Coimbra. While studying for his degree, José became interested in processor architectures and real-time systems. After a year working in robotics (ISR-Coimbra), José finally moved into ISEP's CISTER unit to carry out his PhD studies in real-time systems.

Papers: Tightening the Bounds on Feasible Preemption Points (pdf), The Worst-Case Execution Time Problem - overview of methods and survey of tools (pdf), Preemption Points Placement for Sporadic Tasks (pdf), A New Notion of Useful Cache Block to Improve the Bounds of Cache-Related Preemption Delay (pdf),Scalable Precision Cache Analysis for Real-Time Software (pdf) Scheduling Real-Time Applications in an Open Environment (pdf) Bounding Cache-Related Preemption Delay for Real-Time Systems (pdf) Bounding Preemption Delay within Data Cache Reference Patterns for Real-Time Tasks (pdf) Accurate Estimation of Cache-Related Preemption Delay (pdf)


Talk slides: pdf

June 4 - Claro Noda, ISEP, Portugal - Fine-grained network time synchronization using reference broadcasts¶

Talk abstract:Recent advances in miniaturization and low-cost, low-power design have led to active research in large-scale networks of small, wireless, low-power sensors and actuators. Time synchronization is critical in sensor networks for diverse purposes including sensor data fusion, coordinated actuation, and power-efficient duty cycling. Though the clock accuracy and precision requirements are often stricter than in traditional distributed systems, strict energy constraints limit the resources available to meet these goals.We present Reference-Broadcast Synchronization, a scheme in which nodes send reference beacons to their neighbors using physical-layer broadcasts. A reference broadcast does not contain an explicit timestamp; instead, receivers use its arrival time as a point of reference for comparing their clocks. In this paper, we use measurements from two wireless implementations to show that removing the sender's nondeterminism from the critical path in this way produces high-precision clock agreement (1.85 ± 1.28μsec, using off-the-shelf 802.11 wireless Ethernet), while using minimal energy. We also describe a novel algorithm that uses this same broadcast property to federate clocks across broadcast domains with a slow decay in precision (3.68 ± 2.57μsec after 4 hops). RBS can be used without external references, forming a precise relative timescale, or can maintain microsecond-level synchronization to an external timescale such as UTC. We show a significant improvement over the Network Time Protocol (NTP) under similar conditions.

Speaker Bio.:Claro Noda graduated in Physics from University of Havana, Cuba in 1996. He worked in Scientific Instrumentation at the Superconductivity Laboratory, IMRE (1996-2001) where he completed his Master in Physical Sciences in 2000 and later continued research activities at the "Henri Poincaré" Complex Systems Group. He has also taught at the General Physics Department in the Faculty of Physics in Havana (2005-2008). Currently he's a MAP-Tele PhD student at University of Minho and a researcher at CISTER/ISEP, Portugal.

Paper: Fine-grained network time synchronization using reference broadcasts (pdf)

July 2 - Ricardo Garibay-Martínez, ISEP, Portugal - Integrating Multimedia Applications in Hard Real-Time Systems¶

Talk abstract:This paper focuses on the problem of providing efficient run-time support to multimedia applications in a real-time system, where two types of tasks can coexist simultaneously: multimedia soft real-time tasks and hard real-time tasks. Hard tasks are guaranteed based on worst case execution times and minimum interarrival times, whereas multimedia and soft tasks are served based on mean parameters. The paper describes a server-based mechanism for scheduling soft and multimedia tasks without jeopardizing the a priori guarantee of hard real-time activities. The performance of the proposed method is compared with that of similar service mechanisms through extensive simulation experiments and several multimedia applications have been implemented on the HARTIK kernel.

Speaker Bio.:Ricardo Garibay-Martínez was born on 1984 in Morelia, Mexico. Ricardo received his Bachelors Degree from Morelia Institute of Technology (ITM) in 2007 and finished his Master of Science in Computer Science from Centre for Scientific Research and Higher Education of Ensenada (CICESE), Mexico. He has experience working as a lecturer and as a researcher for PEMEX Petroleum Company. Since 2007, he has been working in the area of Adaptive Resource Management in Distributed Dynamic Real-Time Systems. Currently, he is working as a researcher and PhD student in CISTER/IPP-HURRAY Research unit. His current research interests are Adaptive RT Systems, RT Software and Multi-core Systems.

Paper: Integrating Multimedia Applications in Hard Real-Time Systems (pdf)

July 9 - Artem Burmyakov, ISEP, Portugal - Principles of Real-Time Programming¶

July 16 - Maryam Vahabi, ISEP, Portugal - Wireless Sensor Networks for Habitat Monitoring¶

July 23 - Dakshina Dasari, ISEP, Portugal - Bounds on Multiprocessing Timing Anomalies¶

September 10 - Aida Ehyaei, ISEP, Portugal - Towards Controllable Distributed Real-Time Systems with Feasible Utilization Control¶

September 17 - José Marinho, ISEP, Portugal - Integrated Resource Management and Scheduling with Multi-Resource Constraints Integrated Resource Management and Scheduling with Multi-Resource Constraints¶

September 24 - Paulo Baltarejo Sousa, ISEP, Portugal - Scheduling Algorithms for Multiprocessors in a Hard Real-Time Environment¶

October 1 - Hossein Fotouhi, ISEP, Portugal - Emerging Challenges: Mobile Networking for Smart Dust¶

October 8 - Gurulingesh Raravi, ISEP, Portugal - Multiprocessor On-Line Scheduling of Hard-Real-Time Tasks¶

October 15 - Eduardo Tovar (to be confirmed), ISEP, Portugal - Highly Scalable Aggregate Computations in Cyber-Physical Systems: Physical Environment Meets Communication Protocols¶

October 22 - Muhammad Ali Awan, ISEP, Portugal - Improving Soft Real-Time Performance Through Better Slack Reclaiming¶

October 29 - António Barros, ISEP, Portugal - Programming Execution-Time Servers in Ada 2005¶

November 5 - Ricardo Severino, ISEP, Portugal - Computing Needs Time¶