Pub Date : 1995-12-05DOI: 10.1109/REAL.1995.495209
M. Natale, J. Stankovic
This paper presents a non-conventional scheduling approach for distributed static systems where tasks are periodic and have arbitrary deadlines, precedence, and exclusion constraints. The solution presented in this work not only creates feasible schedules, but also minimizes jitter for periodic tasks. The problem of scheduling real-time tasks with minimum jitter is particularly important in many control applications, nevertheless, it has been rarely studied in the scientific literature. We present a general framework consisting of an abstract architecture model and a general programming model. We show how to design a surprisingly simple and flexible scheduling method based on simulated annealing and present some experimental results.
{"title":"Applicability of simulated annealing methods to real-time scheduling and jitter control","authors":"M. Natale, J. Stankovic","doi":"10.1109/REAL.1995.495209","DOIUrl":"https://doi.org/10.1109/REAL.1995.495209","url":null,"abstract":"This paper presents a non-conventional scheduling approach for distributed static systems where tasks are periodic and have arbitrary deadlines, precedence, and exclusion constraints. The solution presented in this work not only creates feasible schedules, but also minimizes jitter for periodic tasks. The problem of scheduling real-time tasks with minimum jitter is particularly important in many control applications, nevertheless, it has been rarely studied in the scientific literature. We present a general framework consisting of an abstract architecture model and a general programming model. We show how to design a surprisingly simple and flexible scheduling method based on simulated annealing and present some experimental results.","PeriodicalId":231426,"journal":{"name":"Proceedings 16th IEEE Real-Time Systems Symposium","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130119247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-12-05DOI: 10.1109/REAL.1995.495222
M. Lehr, Young-Kuk Kim, S. Son
Previous work in real-time database management systems (RT-DBMS) has primarily based on simulation. This paper discusses how current real-time technology has been applied to architect an actual RT-DBMS on a real-time microkernel operating system. A real RT-DBMS must confront many practical issues which simulations typically ignore race conditions, concurrency, and asynchrony. The challenge of constructing a RT-DBMS is divided into three basic problems: dealing with resource contention, dealing with data contention, and enforcing timing constraints. In this paper, we present our approaches to each problem.
{"title":"Managing contention and timing constraints in a real-time database system","authors":"M. Lehr, Young-Kuk Kim, S. Son","doi":"10.1109/REAL.1995.495222","DOIUrl":"https://doi.org/10.1109/REAL.1995.495222","url":null,"abstract":"Previous work in real-time database management systems (RT-DBMS) has primarily based on simulation. This paper discusses how current real-time technology has been applied to architect an actual RT-DBMS on a real-time microkernel operating system. A real RT-DBMS must confront many practical issues which simulations typically ignore race conditions, concurrency, and asynchrony. The challenge of constructing a RT-DBMS is divided into three basic problems: dealing with resource contention, dealing with data contention, and enforcing timing constraints. In this paper, we present our approaches to each problem.","PeriodicalId":231426,"journal":{"name":"Proceedings 16th IEEE Real-Time Systems Symposium","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133966143","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-12-05DOI: 10.1109/REAL.1995.495208
H. Kopetz, Martin Oberkönig, C. Ebner, A. Krüger, D. Millinger, Roman Nossal-Tüyeni, A. Schedl
The time-triggered (TT) architecture approach supports the spatial partitioning of a large, distributed real-time system into a set of autonomous subsystems with small control-free data-sharing interfaces between them. This paper presents such a TT architecture and gives a detailed description of the interface between an autonomous time-triggered communication subsystem based on the TTP protocol and the host computer within a node of this architecture. This interface acts as a temporal firewall that eliminates the possibility of control error propagation from one subsystem to another subsystem. It thus facilitates the independent development and validation of the subsystems and supports the composability of the distributed architecture with respect to timeliness, validation, and certification.
{"title":"The design of large real-time systems: the time-triggered approach","authors":"H. Kopetz, Martin Oberkönig, C. Ebner, A. Krüger, D. Millinger, Roman Nossal-Tüyeni, A. Schedl","doi":"10.1109/REAL.1995.495208","DOIUrl":"https://doi.org/10.1109/REAL.1995.495208","url":null,"abstract":"The time-triggered (TT) architecture approach supports the spatial partitioning of a large, distributed real-time system into a set of autonomous subsystems with small control-free data-sharing interfaces between them. This paper presents such a TT architecture and gives a detailed description of the interface between an autonomous time-triggered communication subsystem based on the TTP protocol and the host computer within a node of this architecture. This interface acts as a temporal firewall that eliminates the possibility of control error propagation from one subsystem to another subsystem. It thus facilitates the independent development and validation of the subsystems and supports the composability of the distributed architecture with respect to timeliness, validation, and certification.","PeriodicalId":231426,"journal":{"name":"Proceedings 16th IEEE Real-Time Systems Symposium","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131659962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-12-05DOI: 10.1109/REAL.1995.495196
T. Henzinger, Pei-Hsin Ho, H. Wong-Toi
We describe a new implementation of HYTECH, a symbolic model checker for hybrid systems. Given a parametric description of an embedded system as a collection of communicating automata, HYTECH automatically computes the conditions on the parameters under which the system satisfies its safety and timing requirements. While the original HYTECH prototype was based on the symbolic algebra tool Mathematica, the new implementation is written in C++ and builds on geometric algorithms instead of formula manipulation. The new HYTECH offers a cleaner and more expressive input language, greater portability, superior performance (typically two to three orders of magnitude), and new features such as diagnostic error-trace generation. We illustrate the effectiveness of the new implementation by applying HYTECH to the automatic parametric analysis of the generic railroad crossing benchmark problem and to an active structure control algorithm.
{"title":"HYTECH: the next generation","authors":"T. Henzinger, Pei-Hsin Ho, H. Wong-Toi","doi":"10.1109/REAL.1995.495196","DOIUrl":"https://doi.org/10.1109/REAL.1995.495196","url":null,"abstract":"We describe a new implementation of HYTECH, a symbolic model checker for hybrid systems. Given a parametric description of an embedded system as a collection of communicating automata, HYTECH automatically computes the conditions on the parameters under which the system satisfies its safety and timing requirements. While the original HYTECH prototype was based on the symbolic algebra tool Mathematica, the new implementation is written in C++ and builds on geometric algorithms instead of formula manipulation. The new HYTECH offers a cleaner and more expressive input language, greater portability, superior performance (typically two to three orders of magnitude), and new features such as diagnostic error-trace generation. We illustrate the effectiveness of the new implementation by applying HYTECH to the automatic parametric analysis of the generic railroad crossing benchmark problem and to an active structure control algorithm.","PeriodicalId":231426,"journal":{"name":"Proceedings 16th IEEE Real-Time Systems Symposium","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131668545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-12-05DOI: 10.1109/REAL.1995.495211
M. Spuri, G. Buttazzo, F. Sensini
When hard periodic and firm aperiodic tasks are jointly scheduled in the same system, the processor workload can vary according to the arrival times of aperiodic requests. In order to guarantee the schedulability of the periodic task set, in overload conditions some aperiodic tasks must be rejected. In this paper we propose a technique that, in overload conditions, adds robustness to the joint scheduling of periodic and aperiodic tasks in systems with dynamic priorities. Our technique is based on an aperiodic server, called total bandwidth server, already proven effective in a previous work. Here the algorithm is first extended to efficiently handle firm aperiodic tasks and then integrated with a robust guarantee mechanism that allows to achieve graceful degradation in case of transient overloads. Extensive simulations show that the proposed new algorithm is effective in all workload conditions.
{"title":"Robust aperiodic scheduling under dynamic priority systems","authors":"M. Spuri, G. Buttazzo, F. Sensini","doi":"10.1109/REAL.1995.495211","DOIUrl":"https://doi.org/10.1109/REAL.1995.495211","url":null,"abstract":"When hard periodic and firm aperiodic tasks are jointly scheduled in the same system, the processor workload can vary according to the arrival times of aperiodic requests. In order to guarantee the schedulability of the periodic task set, in overload conditions some aperiodic tasks must be rejected. In this paper we propose a technique that, in overload conditions, adds robustness to the joint scheduling of periodic and aperiodic tasks in systems with dynamic priorities. Our technique is based on an aperiodic server, called total bandwidth server, already proven effective in a previous work. Here the algorithm is first extended to efficiently handle firm aperiodic tasks and then integrated with a robust guarantee mechanism that allows to achieve graceful degradation in case of transient overloads. Extensive simulations show that the proposed new algorithm is effective in all workload conditions.","PeriodicalId":231426,"journal":{"name":"Proceedings 16th IEEE Real-Time Systems Symposium","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123548945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-12-05DOI: 10.1109/REAL.1995.495202
Sunondo Ghosh, R. Melhem, D. Mossé
We present a scheme to guarantee that the execution of real-time tasks can tolerate transient and intermittent faults assuming any queue-based scheduling technique. The scheme is based on reserving sufficient slack: in a schedule such that a task can be re-executed before its deadline without compromising guarantees given to other tasks. Only enough slack is reserved in the schedule to guarantee fault tolerance if at most one fault occurs within a time interval. This results in increased schedulability and a very low percentage of deadline misses even if no restriction is placed on the fault separation. We provide two algorithms to solve the problem of adding fault tolerance to a queue of real-time tasks. The first is a dynamic programming optimal solution and the second is a greedy heuristic which closely approximates the optimal.
{"title":"Enhancing real-time schedules to tolerate transient faults","authors":"Sunondo Ghosh, R. Melhem, D. Mossé","doi":"10.1109/REAL.1995.495202","DOIUrl":"https://doi.org/10.1109/REAL.1995.495202","url":null,"abstract":"We present a scheme to guarantee that the execution of real-time tasks can tolerate transient and intermittent faults assuming any queue-based scheduling technique. The scheme is based on reserving sufficient slack: in a schedule such that a task can be re-executed before its deadline without compromising guarantees given to other tasks. Only enough slack is reserved in the schedule to guarantee fault tolerance if at most one fault occurs within a time interval. This results in increased schedulability and a very low percentage of deadline misses even if no restriction is placed on the fault separation. We provide two algorithms to solve the problem of adding fault tolerance to a queue of real-time tasks. The first is a dynamic programming optimal solution and the second is a greedy heuristic which closely approximates the optimal.","PeriodicalId":231426,"journal":{"name":"Proceedings 16th IEEE Real-Time Systems Symposium","volume":"T164 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125666067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-12-05DOI: 10.1109/REAL.1995.495191
N. Baker, W. Harris, C. Wallace, R. McClatchey, J. Goff
The CERN Research and Development project (RD-38), named CICERO, aims to identify and design the main building blocks of a generic control information system based on distributed objects. The project is producing an integrating framework (named Cortex) into which user real-time control objects will ultimately be plugged (and played) and a control information system to support its configuration and management. Development of Cortex is following the ESA PSS-05-02 software engineering standards. Cortex is providing an environment which allows real-time control systems to share information, control and analysis functions which presents a uniform human interface; which permits upgrades and additions without code modification; and which is sufficiently generic to allow its use both by existing or future control systems at CERN and by industrial real time control systems. It provides both high level data access, abstracting objects to a level appropriate for on-line control and low level data access to allow views of experimental sub-components for detailed real-time control. Additionally, the Cortex system shall enable developers to grow their control systems from a lab-based test system to the complete experimental system and is therefore both scaleable and flexible to change. Technical solutions are being identified in CICERO which could later be the major components of a basic turnkey control system for future medium to large scale HEP experiments and accelerators as well as for industrial control systems. This paper outlines the modelling concepts behind Cortex.
{"title":"Modelling a real time control system based on distributed objects","authors":"N. Baker, W. Harris, C. Wallace, R. McClatchey, J. Goff","doi":"10.1109/REAL.1995.495191","DOIUrl":"https://doi.org/10.1109/REAL.1995.495191","url":null,"abstract":"The CERN Research and Development project (RD-38), named CICERO, aims to identify and design the main building blocks of a generic control information system based on distributed objects. The project is producing an integrating framework (named Cortex) into which user real-time control objects will ultimately be plugged (and played) and a control information system to support its configuration and management. Development of Cortex is following the ESA PSS-05-02 software engineering standards. Cortex is providing an environment which allows real-time control systems to share information, control and analysis functions which presents a uniform human interface; which permits upgrades and additions without code modification; and which is sufficiently generic to allow its use both by existing or future control systems at CERN and by industrial real time control systems. It provides both high level data access, abstracting objects to a level appropriate for on-line control and low level data access to allow views of experimental sub-components for detailed real-time control. Additionally, the Cortex system shall enable developers to grow their control systems from a lab-based test system to the complete experimental system and is therefore both scaleable and flexible to change. Technical solutions are being identified in CICERO which could later be the major components of a basic turnkey control system for future medium to large scale HEP experiments and accelerators as well as for industrial control systems. This paper outlines the modelling concepts behind Cortex.","PeriodicalId":231426,"journal":{"name":"Proceedings 16th IEEE Real-Time Systems Symposium","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126207827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-12-05DOI: 10.1109/REAL.1995.495214
Kevin A. Kettler, J. Strosnider
This paper develops formal scheduling models for several common system bus architectures used in PC and workstation systems. The scheduling models include fixed priority, round robin, and hybrid bus scheduling policies. The models provide a quantitative means to explore the real-time design space for each of the buses. This paper provides a simple approach for the creation of bus scheduling models which can be used effectively by a bus designer or system user to improve real-time bus performance. The step by step process of model development is presented. In addition, an application modeling methodology is described which separates the application requirements from the bus model. The utility of the scheduling models is demonstrated by analyzing several common system buses.
{"title":"Modeling bus scheduling policies for real-time systems","authors":"Kevin A. Kettler, J. Strosnider","doi":"10.1109/REAL.1995.495214","DOIUrl":"https://doi.org/10.1109/REAL.1995.495214","url":null,"abstract":"This paper develops formal scheduling models for several common system bus architectures used in PC and workstation systems. The scheduling models include fixed priority, round robin, and hybrid bus scheduling policies. The models provide a quantitative means to explore the real-time design space for each of the buses. This paper provides a simple approach for the creation of bus scheduling models which can be used effectively by a bus designer or system user to improve real-time bus performance. The step by step process of model development is presented. In addition, an application modeling methodology is described which separates the application requirements from the bus model. The utility of the scheduling models is demonstrated by analyzing several common system buses.","PeriodicalId":231426,"journal":{"name":"Proceedings 16th IEEE Real-Time Systems Symposium","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129304279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-12-05DOI: 10.1109/REAL.1995.495213
J. Hou, Kar Shun Tsoi
The distributed queue dual bus (DQDB) protocol has been jointly adopted by IEEE and ANSI as a standard (IEEE802.6) for metropolitan area networks (MANs). As such, how to provide various services in the DQDB protocol has attracted increasing attention. In particular, how to guarantee the timely delivery of isochronous (real-time) messages with hard deadline constraints is one of the open issues yet to be solved. Previously, we laid a formal basis for allocating pre-arbitrated (PA) slots to isochronous message streams in DQDB networks and devised a slot allocation scheme to statically establish a set of isochronous message streams at system initialization. In this paper, we complement our previous work and propose a dynamic channel setup and tear-down scheme for DQDB networks. The resulting channel establishment and termination procedures are simple, can be easily implemented in DQDB networks, and do not require any changes in the current DQDB standards.
{"title":"Dynamic real-time channel setup and tear-down in DQDB networks","authors":"J. Hou, Kar Shun Tsoi","doi":"10.1109/REAL.1995.495213","DOIUrl":"https://doi.org/10.1109/REAL.1995.495213","url":null,"abstract":"The distributed queue dual bus (DQDB) protocol has been jointly adopted by IEEE and ANSI as a standard (IEEE802.6) for metropolitan area networks (MANs). As such, how to provide various services in the DQDB protocol has attracted increasing attention. In particular, how to guarantee the timely delivery of isochronous (real-time) messages with hard deadline constraints is one of the open issues yet to be solved. Previously, we laid a formal basis for allocating pre-arbitrated (PA) slots to isochronous message streams in DQDB networks and devised a slot allocation scheme to statically establish a set of isochronous message streams at system initialization. In this paper, we complement our previous work and propose a dynamic channel setup and tear-down scheme for DQDB networks. The resulting channel establishment and termination procedures are simple, can be easily implemented in DQDB networks, and do not require any changes in the current DQDB standards.","PeriodicalId":231426,"journal":{"name":"Proceedings 16th IEEE Real-Time Systems Symposium","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116388092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-12-05DOI: 10.1109/REAL.1995.495210
Sanjoy Baruah
The issue of temporal fairness in periodic real-time scheduling is considered. It is argued that such fairness is often a desirable characteristic in real-time schedules. A concrete criterion for temporal fairness-pfairness-is described. The weight-monotonic scheduling algorithm, a static priority scheduling algorithm for generating pfair schedules, is presented and proven correct. A feasibility test is presented which, if satisfied by a system of periodic tasks, ensures that the weight-monotonic scheduling algorithm will schedule the system in a pfair manner.
{"title":"Fairness in periodic real-time scheduling","authors":"Sanjoy Baruah","doi":"10.1109/REAL.1995.495210","DOIUrl":"https://doi.org/10.1109/REAL.1995.495210","url":null,"abstract":"The issue of temporal fairness in periodic real-time scheduling is considered. It is argued that such fairness is often a desirable characteristic in real-time schedules. A concrete criterion for temporal fairness-pfairness-is described. The weight-monotonic scheduling algorithm, a static priority scheduling algorithm for generating pfair schedules, is presented and proven correct. A feasibility test is presented which, if satisfied by a system of periodic tasks, ensures that the weight-monotonic scheduling algorithm will schedule the system in a pfair manner.","PeriodicalId":231426,"journal":{"name":"Proceedings 16th IEEE Real-Time Systems Symposium","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116954667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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