This survey covers hard real-time scheduling algorithms and schedulability analysis techniques for homogeneous multiprocessor systems. It reviews the key results in this field from its origins in the late 1960s to the latest research published in late 2009. The survey outlines fundamental results about multiprocessor real-time scheduling that hold independent of the scheduling algorithms employed. It provides a taxonomy of the different scheduling methods, and considers the various performance metrics that can be used for comparison purposes. A detailed review is provided covering partitioned, global, and hybrid scheduling algorithms, approaches to resource sharing, and the latest results from empirical investigations. The survey identifies open issues, key research challenges, and likely productive research directions.

/pdf/a-survey-of-hard-real-time-scheduling-for-multiprocessor-313o35g6ho.pdf

A survey of hard real-time scheduling for multiprocessor systems

A remote controlled robot system that includes a robot and a remote control station. The robot includes a binaural microphone system that is coupled to a speaker system of the remote control station. The binaural microphone system may include a pair of microphones located at opposite sides of a robot head. the location of the microphones roughly coincides with the location of ears on a human body. Such microphone location creates a mobile robot that more effectively simulates the tele-presence of an operator of the system. The robot may include two different microphone systems and the ability to switch between systems. For example, the robot may also include a zoom camera system and a directional microphone. The directional microphone may be utilized to capture sound from a direction that corresponds to an object zoomed upon by the camera system.

Mobile tele-presence system with a microphone system

A remote controlled robot with a head that supports a monitor and is coupled to a mobile platform. The mobile robot also includes an auxiliary camera coupled to the mobile platform by a boom. The mobile robot is controlled by a remote control station. By way of example, the robot can be remotely moved about an operating room. The auxiliary camera extends from the boom so that it provides a relatively close view of a patient or other item in the room. An assistant in the operating room may move the boom and the camera. The boom may be connected to a robot head that can be remotely moved by the remote control station.

Telepresence robot with a camera boom

A mobile robot that includes a drive system, a controller in communication with the drive system, and a volumetric point cloud imaging device supported above the drive system at a height of greater than about one feet above the ground and directed to be capable of obtaining a point cloud from a volume of space that includes a floor plane in a direction of movement of the mobile robot. The controller receives point cloud signals from the imaging device and issues drive commands to the drive system based at least in part on the received point cloud signals.

Mobile human interface robot

From the Publisher:
Real-Time Systems is both a valuable reference for professionals and an advanced text for Computer Science and Computer Engineering students. 

Real world real-time applications based on research and practice

State-of-the-art algorithms and methods for validation

Methods for end-to-end scheduling and resource management

More than 100 illustrations to enhance understanding

Comprehensive treatment of the technology known as RMA (rate-monotonic analysis) methods

A supplemental Companion Website www.prenhall.com/liu

http://user.it.uu.se/~yi/courses/rts/dvp-rts-08/notes/Course-INFO.pdf

Real-Time Systems

This paper presents a new algorithm for scheduling of sporadic task systems with arbitrary deadlines on identical multiprocessor platforms. The algorithm is based on the concept of semi-partitioned scheduling, in which most tasks are fixed to specific processors, while a few tasks migrate across processors. Particularly, we design the algorithm so that tasks are qualified to migrate only if a task set cannot be partitioned any more, and such migratory tasks migrate from one processor to another processor only once in each period. The scheduling policy is then subject to Earliest Deadline First. Simulation results show that the algorithm delivers competitive scheduling performance to the state-of-the-art, with a smaller number of context switches.

/pdf/semi-partitioned-scheduling-of-sporadic-task-systems-on-1w88q6h6ei.pdf

Semi-partitioned Scheduling of Sporadic Task Systems on Multiprocessors

This paper presents a new algorithm for fixed-priority scheduling of sporadic task systems on multiprocessors.The algorithm is categorized to such a scheduling class that qualifies a few tasks to migrate across processors, while most tasks are fixed to particular processors. We design the algorithm so that a task is qualified to migrate, only if it cannot be assigned to any individual processors, in such a way that it is never returned to the same processor within the same period, once it is migrated from one processor to another processor. The scheduling policy is then conformed to Deadline Monotonic. According to the simulation results, the new algorithm significantly outperforms the traditional fixed-priority algorithms in terms of schedulability.

Semi-partitioned Fixed-Priority Scheduling on Multiprocessors

This paper presents a real-time scheduling algorithm with high schedulability and few preemptions for multiprocessor systems. The algorithm is based on an unorthodox method called portioned scheduling that assigns each task to a particular processor like partitioned scheduling but can split a task into two processors if there is not enough capacity remaining on a processor. We describe an algorithm for assigning tasks to processors as well as an algorithm for scheduling the assigned tasks on per-processor. The schedulability analysis provides a formula to calculate the upper bound of the schedulable per-processor utilization for the algorithm. We then prove that the least upper bound of the whole system utilization is 50%. In addition, we propose heuristic procedures to improve schedulability. The simulation results show that the algorithm can often successfully schedule a task set with system utilization much higher than 50%, though the least upper bound is 50%. We also show that the algorithm achieves higher schedulability with fewer preemptions compared to the existing algorithms.

http://www.ny.ics.keio.ac.jp/research/publications/draft/shinpei_RTCSA07_draft.pdf

Real-Time Scheduling with Task Splitting on Multiprocessors

This paper presents an EDF-based algorithm, called Earliest Deadline Deferrable Portion (EDDP), for efficient scheduling of recurrent real-time tasks on multiprocessor systems. The design of EDDP is based on the portioned scheduling technique which classifies each task into a fixed task or a migratable task. A fixed task is scheduled on the dedicated processor without migrations. A migratable task is meanwhile permitted to migrate between the particular two processors. In order to curb the cost of task migrations, EDDP makes at most M -- 1 migratable tasks on M processors. The scheduling analysis derives the condition for a given task set to be schedulable. It is also proven that no tasks ever miss deadlines, if the system utilization does not exceed 65%. Beyond the theoretical analysis, the effectiveness of EDDP is evaluated through simulation studies. Simulation results show that EDDP achieves high system utilization with a small number of preemptions, compared with the traditional EDF-based algorithms.

Portioned EDF-based scheduling on multiprocessors

Extended T-N plane abstraction (E-TNPA) proposed in this paper realizes work-conserving and efficient optimal real-time scheduling on multiprocessors relative to the original T-N plane abstraction (TNPA). Additionally a scheduling algorithm named NVNLF (no virtual nodal laxity first) is presented for E-TNPA. E-TNPA and NVNLF relax the restrictions of TNPA and the traditional algorithm LNREF, respectively. Arbitrary tasks can be preferentially executed by both tie-breaking rules and time apportionment policies in accordance with various system requirements with several restrictions. Simulation results show that E-TNPA significantly reduces the number of task preemptions as compared to TNPA.

https://www.ny.ics.keio.ac.jp/research/publications/draft/funaoka_ECRTS08_draft.pdf

Nobuyuki Yamasaki

Papers

Semi-partitioned Scheduling of Sporadic Task Systems on Multiprocessors

Semi-partitioned Fixed-Priority Scheduling on Multiprocessors

Real-Time Scheduling with Task Splitting on Multiprocessors

Portioned EDF-based scheduling on multiprocessors

Work-Conserving Optimal Real-Time Scheduling on Multiprocessors