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(searched for: doi:10.1109/real.1999.818850)
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Anselm Busse, Reinhardt Karnapke, Hans-Ulrich Heiss
Abstract:
Many-Core systems and heterogeneous systems are getting more and more common and may soon enter the mainstream market. To harvest their capabilities to their full potential, the runtime system's scheduling policies have to be adapted and, in many cases, tailored to the specific system. The runtime system can be both an operating system or management infrastructure of an infrastructure as a service (IaaS) platform. Developing, implementing, and testing those scheduling policies is a challenging task in general. In this work we present CoBaS, a component based scheduling framework for multi and many-core runtime systems. The main purpose of CoBaS is the simplification of the scheduling policy implementation and an increased code reuse to save time during development. CoBaS uses a novel approach to reach that goal. It allows the breakdown of the policy implementation into several components that can be reused. Through composition, a fast prototyping, testing and evaluation of new scheduling policies is possible without implementing every functional part again. CoBaS uses an event based approach to distribute information about system states and state changes between the runtime system and components as well as between components themselves. Furthermore, it has a facility to hand over ordered task sets between components. We have adapted both the Linux and Free BSD kernel to use CoBaS by completely removing the native scheduler. The integration of CoBaS into those kernels shows the feasibility of our approach.
Purnima Singhal, Amit Kumar, Upendra Ghintala,
Abstract:
The feasible execution of real time tasks over a platform majorly depends upon the scheduling policies to be used. Also, different task domains comply to different resource requirements. Allocating resources optimally according to the task requirements is a core challenge to the real time systems community. This paper discusses an approach where we leverage a generalized non-real time system to develop an integrated schedule for real time tasks by extending the control for resource allocation to the user level. A major advantage of this framework is that it does not involve any modifications to the underlying kernel code or the use of patches. In our framework, two levels of scheduling are maintained, where at the base level the task schedule is decided by the kernel internally, and at the extended level, the user determines a separate schedule. Both the schedules are maintained inside the kernel. Each schedule is preceded by a schedulability test which governs the feasibility of execution of the incoming task set.
Mikael Asberg, Thomas Nolte, Shinpei Kato, Ragunathan Rajkumar
Abstract:
Scheduling theory and algorithms have been well studied in the real-time systems literature. Many useful approaches and solutions have appeared in different problem domains. While their theoretical effectiveness has been extensively discussed, the community is now facing implementation challenges that show the impact of the algorithms in practice. In this paper, we propose a scheduler framework, called ExSched, which enables different schedulers to be developed for different operating system (OS) platforms without any modifications to the OS itself, using a unified interface. The framework will easily keep up with changes in the kernel since it is only dependent on a few kernel primitives. The usefulness of this framework is that scheduling policies can be implemented as external plug-ins. They can simply use the ExSched interface instead of platform-dependent functions, since platform details are abstracted by ExSched. The advantage for industry is that they would more easily keep up with new kernel versions since ExSched does not require patches. The advantage for academia is that we could focus on the development of schedulers instead of tedious and time-consuming installations of patched kernels. Our prototype implementation of ExSched supports Linux and Vx Works and it comes with example schedulers which include hierarchical and multi-core schedulers in addition to traditional fixed-priority scheduling (FPS) and earliest deadline first (EDF) algorithms.
Shinpei Kato, Ragunathan Rajkumar, Yutaka Ishikawa
Abstract:
Modern real-time systems increasingly operate with multiple interactive applications. While these systems often require reliable quality of service (QoS) for the applications, even under heavy workloads, many existing CPU schedulers are not very capable of satisfying such requirements. In this paper, we design and implement an Advanced Interactive and Real-time Scheduler, called AIRS. AIRS is aimed at supporting systems that run multiple interactive real-time applications, particularly on multicore platforms. It provides a new CPU reservation mechanism to enhance the QoS of the overall system. The reservation algorithm is based on the prior Constant Bandwidth Server (CBS) algorithm, but is more flexible and efficient, when multiple applications reserve CPU bandwidth. It also provides a new multicore scheduler to improve the absolute CPU bandwidth available for the applications to perform well. The scheduling algorithm is subject to the prior Earliest Deadline First with Window-constraint Migration (EDF-WM) algorithm, but is extended to work with the new CPU reservation mechanism. Experimental evaluation shows that AIRS delivers higher quality to simultaneous playback of multiple movies than the existing real-time scheduler. It also demonstrates that AIRS offers hard timing guarantees for randomly-generated task sets with heavy workloads.
Miao Liu, Duo Liu, Yi Wang, Meng Wang,
IEEE Transactions on Computers, Volume 60, pp 978-991; https://doi.org/10.1109/tc.2010.119

Abstract:
In this paper, we propose to implement hybrid operating systems based on two-level hardware interrupts. We analyze and model the worst-case real-time interrupt latency for RTAI and identify the key component for its optimization. Then, we propose our methodology to implement hybrid operating systems with two-level hardware interrupts by combining the real-time kernel and the time sharing OS (Operating System) kernel. Based on the methodology, we discuss the important issues for the implementation. Finally, we implement a hybrid system called RTLinux-THIN (Real-Time LINUX with Two-level Hardware INterrupts) on the ARM architecture by combining ARM Linux kernel 2.6.9 and μC/OS-II. We conduct experiments on a set of real application programs including mplayer, Bonnie, and iperf, and compare the interrupt latency and interrupt task distributions for RTLinux-THIN (with and without cache locking), RTAI, Linux, and Linux with RT patch on a hardware platform based on Intel PXA270 processor. The results show that our scheme not only provides an easy method for implementing hybrid systems but also achieves the performance improvement for both the time sharing and real-time subsystems.
Yudong Wang, Jiong Zhang, Lihong Shang, Xiang Long, Huihua Jin
Abstract:
Aimed at the needs for scheduling real-time tasks in the environment of open real-time system and embedded system, a scheduling mechanism based on messages has been suggested and applied on the Xen virtual machine, and a Multi-Real-Time-Task model based on VCPU is established. Influence on the real-time scheduling is analyzed and solutions will be given. Experiment results prove that scheduling based on this mechanism works well, since in current experiment environment the response time of compute-intensive real-time task is less than 20us, and the response time of event-driven real-time task is less than 30us, both results are quite stable.
, Renato Cerqueira
Concurrency and Computation: Practice and Experience, Volume 22, pp 278-294; https://doi.org/10.1002/cpe.1473

The publisher has not yet granted permission to display this abstract.
Dian-Gang Wang, Yan Sheng Cai, Hong Guo, Ze Gui Ying, Si-Yuan Wu
Abstract:
The rapid development of Internet technology brings people not only great convenience but also many potential safety hazards. This paper studied and implemented embedded Linux operating system first and then introduced the network topology and transmission mechanism of system and identity authentication protocol and key exchange protocol of platform, subsequently introduced the data encryption algorithm of platform and utilized OpenSSL cryptographic algorithm library to realize data encryption, finally introduced the design of client software of platform.
Xue-Yu Hong, Ling Zhang,
Abstract:
To well support the real-time requirement from applications, we enhance the real-time ability in Linux kernel through two new kernel mechanisms. Firstly, we present a new microsecond-level timer mechanism based on UTIME provided by Kurt-Linux, but different from it. The new timing implementation provides more flexible mechanism to support the different-grained timing requirement, as well as more flexible and preferential management of microsecond-level timers. Secondly, we present a new interrupt handler to reduce the kernel delay, which makes it possible scheduling interrupt handler with other processes under the system scheduler. Therefore, making interrupt routine under control is achieved. The experiments show that the improvements are distinct and significant.
Chih-Yuan Huang, ,
Abstract:
Universal Serial Bus (USB) is a popular standard for PC peripheral devices because of its versatile peripheral interconnection specifications. USB not only provides simplified hardware connectors but also supports for various bus traffics, such as isochronous and bulk transfer activities. Although the USB specifications provide a way for users to specify the upper bound on the number of bytes for each data transfer in a 1ms time frame, little work is done to provide QoS guarantees for devices (e.g., the lower bound on the bytes for each device type in a 1ms time frame) and a mechanism in enforcing the guarantees. In this paper we propose a cyclic-executive-based bandwidth reservation and scheduling method to support QoS guarantees over USB, especially for those isochronous bus activities. The proposed bandwidth reservation and scheduling method could reserve USB bandwidth for devices in an on-demand fashion. The capability of the proposed scheme was shown by the implementation and demonstration of a USB-based surveillance system prototype which adopted the proposed scheme.
, Kwei-Jay Lin
Abstract:
Web services are self contained and self described modular applications that can be published, discovered and employed on the Web. Many standard protocols supporting Web services have been adopted and more are being proposed. We study the issue on providing intelligent Web services. We propose the enhancement of Web service functionalities by deploying software agents on both server side and/or client side. Our goal of designing the WISE Web service architecture is to provide a working middle ground between the current Web service standards and the semantic Web architecture. The WISE software agent architecture for Web services is presented. We discuss the design issues of WISE. We also present the QoS management protocol and algorithm that can be used by WISE servers.
D. Andrews, D. Niehaus, Andrews D.
Abstract:
Advances in fabrication techniques are now enabling new hybrid CPU/FFPGA computing resources to be integrated onto a single chip. While these new hybrids promise significant performance increases through the customization of massive gate level parallelism, their full potential will not be reached until a suitable computational framework has been developed. We believe that the computational framework should provide a unified model that brings the FPGA and CPU based components under a common programming model for MPP developers. In this paper, we discuss extending the thread programming model to support hybrid CPU and FPGA computational components to allow systems programmers to access the MPP level of parallelism potential of the FPGA, but within a familiar and understood programming model. Author(s) Andrews, D. Inf. Technol. & Telecommun. Center, Kansas Univ., Lawrence, KS, USA Niehaus, D.
I. Pyarali, D.C. Schmidt, R.K. Cytron
Proceedings of the IEEE, Volume 91, pp 1070-1085; https://doi.org/10.1109/jproc.2003.814616

Abstract:
End-to-end predictability of remote operations is essential for many fixed-priority distributed real-time and embedded (DRE) applications, such as command and control systems, manufacturing process control systems, large-scale distributed interactive simulations, and testbeam data acquisition systems. To enhance predictability, the Real-time CORBA specification defines standard middleware features that allow applications to allocate, schedule, and control key CPU, memory, and networking resources necessary to ensure end-to-end quality of service support. This paper provides two contributions to the study of Real-time CORBA middleware for DRE applications. First, we identify potential problems with ensuring predictable behavior in conventional middleware by examining the end-to-end critical code path of a remote invocation and identifying sources of unbounded priority inversions. Experimental results then illustrate how the problems we identify can yield unpredictable behavior in conventional middleware platforms. Second, we present design techniques for ensuring real-time quality of service in middleware. We show how middleware can be redesigned to use nonmultiplexed resources to eliminate sources of unbounded priority inversion. The empirical results in this paper are conducted using TAO, which is widely used and open-source DRE middleware compliant with the Real-time CORBA specification.
Song Wang, Kwei-Jay Lin, Yuchung Wang
Abstract:
A hierarchical scheduling mechanism has been implemented in RED-Linux to integrate different scheduling paradigms together. We extend the concept of group so that the execution budget for jobs in RED-Linux can be managed in a hierarchical way. A budget group contains a set of jobs that share the available budget for the group. The jobs in a budget group could be a normal job or another budget group job, which contains its own group of jobs. Every job has its system budget. But if it belongs to a budget group, the job's budget is also constrained by its group's budget. We discuss how the budget group mechanism is implemented in RED-Linux. We also show how to use the mechanism to implement several schedulers. Author(s) Song Wang Dept. of Electr. & Comput. Eng., California Univ., Irvine, CA, USA Kwei-Jay Lin ; YuChung Wang
J. Serrano, D. Ravier, J. Fraga, V. Orjales, A. Molano
Abstract:
Data acquisition and analysis systems (DAAS) are hardware/software systems with a strong dependence on the features of the process under control, where the amount of data and the sampling frequency of signals to be processed are the main critical aspects of the system. Nowadays DAAS applications are designed according to the specific needs of each particular field. These solutions produce ad hoc software developments, very difficult to reuse. Nevertheless, the basic structure of DAAS is the same across all the different application fields. GEODAS is an EU-funded project whose goal is to develop a framework of reusable, generic components focused on the high-performance DAAS domain. These components capture the generic behaviour of data acquisition systems and offer a new approach for the creation of these systems, which is more modular, reusable, independent from the electronics interface and more platform independent. This paper describes the application of component-based software engineering concepts in an industrial, high-performance, real-time application domain.
Christopher D. Gill, Fred Kuhns, Douglas C. Schmidt, Ron K. Cytron
Published: 5 November 2002
by 10.1007
The publisher has not yet granted permission to display this abstract.
D.G. Schmidt, F. Kuhns
Computer, Volume 33, pp 56-63; https://doi.org/10.1109/2.846319

Abstract:
A growing class of real-time systems require end-to-end support for various quality-of-service (QoS) aspects, including bandwidth, latency, jitter and dependability. Applications include command and control, manufacturing process control, videoconferencing, large-scale distributed interactive simulation, and testbeam data acquisition. These systems require support for stringent QoS requirements. To meet this challenge, developers are turning to distributed object computing middleware, such as the Common Object Request Broker Architecture, an Object Management Group (OMG) industry standard. In complex real-time systems, DOC middleware resides between applications and the underlying operating systems, protocol stacks and hardware. CORBA helps decrease the cycle time and effort required to develop high-quality systems by composing applications using reusable software component services rather than building them entirely from scratch. The Real-Time CORBA specification includes features to manage CPU, network and memory resources. The authors describe the key Real-Time CORBA features that they feel are the most relevant to researchers and developers of distributed real-time and embedded systems.
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