Pub Date : 1995-10-25DOI: 10.1109/RTCSA.1995.528752
V. Tseng, Y. Chin, Wei-Pang Yang
A number of researches on real-time databases have focused on systems where the semantics of transaction time constraints include only deadlines or values that are constant during a transaction's life time. For some real-time applications, the values of transactions may change dynamically with time. Under such circumstances, existing real-time scheduling algorithms may not be applicable. A new real-time scheduling algorithm that can efficiently schedule transactions with time-variant values is proposed. By exploiting the estimated execution time of transactions to estimate the expected values of transactions at completion time, the proposed algorithm can generate a better priority ordering of transactions than the existing algorithms. Moreover, a concurrency control protocol based on conditional-restart is also proposed to reduce the costly restarts. Through performance evaluation, the proposed algorithm is superior to the existing algorithms under various system environments. Some suggestions for scheduling real-time transactions with time-variant values are also presented.
{"title":"Scheduling real-time transactions with dynamic values: a performance evaluation","authors":"V. Tseng, Y. Chin, Wei-Pang Yang","doi":"10.1109/RTCSA.1995.528752","DOIUrl":"https://doi.org/10.1109/RTCSA.1995.528752","url":null,"abstract":"A number of researches on real-time databases have focused on systems where the semantics of transaction time constraints include only deadlines or values that are constant during a transaction's life time. For some real-time applications, the values of transactions may change dynamically with time. Under such circumstances, existing real-time scheduling algorithms may not be applicable. A new real-time scheduling algorithm that can efficiently schedule transactions with time-variant values is proposed. By exploiting the estimated execution time of transactions to estimate the expected values of transactions at completion time, the proposed algorithm can generate a better priority ordering of transactions than the existing algorithms. Moreover, a concurrency control protocol based on conditional-restart is also proposed to reduce the costly restarts. Through performance evaluation, the proposed algorithm is superior to the existing algorithms under various system environments. Some suggestions for scheduling real-time transactions with time-variant values are also presented.","PeriodicalId":111365,"journal":{"name":"Proceedings Second International Workshop on Real-Time Computing Systems and Applications","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116809684","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 : 1995-10-25DOI: 10.1109/RTCSA.1995.528757
Boo-Geum Jung, Young-Jun Cha, Hyung-Hwan Kim, S. Jun, Ju-Hyun Cho
In this paper, we present a dynamic code binding (DCB) method for scalable architecture of operating system in distributed real-time systems. DCB means that binding for calling functions among kernel and servers is executed at run-time through function link tables, unlike traditional binding method through symbol tables. DCB overcomes the restriction that servers can not be replaced when system is running in current micro-kernel structure, therefore improves the systems' extendibility and flexibility. In addition, we use remote system call (RSC) to execute system primitives in remote sites using DCB. This is done at kernel level, so it provides more faster and simple interface than user level RPC. So RSC makes it easy to develop program in distributed real-time systems.
{"title":"Dynamic code binding for scalable operating system in distributed real-time systems","authors":"Boo-Geum Jung, Young-Jun Cha, Hyung-Hwan Kim, S. Jun, Ju-Hyun Cho","doi":"10.1109/RTCSA.1995.528757","DOIUrl":"https://doi.org/10.1109/RTCSA.1995.528757","url":null,"abstract":"In this paper, we present a dynamic code binding (DCB) method for scalable architecture of operating system in distributed real-time systems. DCB means that binding for calling functions among kernel and servers is executed at run-time through function link tables, unlike traditional binding method through symbol tables. DCB overcomes the restriction that servers can not be replaced when system is running in current micro-kernel structure, therefore improves the systems' extendibility and flexibility. In addition, we use remote system call (RSC) to execute system primitives in remote sites using DCB. This is done at kernel level, so it provides more faster and simple interface than user level RPC. So RSC makes it easy to develop program in distributed real-time systems.","PeriodicalId":111365,"journal":{"name":"Proceedings Second International Workshop on Real-Time Computing Systems and Applications","volume":"114 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124555719","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 : 1995-10-25DOI: 10.1109/RTCSA.1995.528763
Prashanth B. Bhat, Y. Lim, V. Prasanna
Embedded signal processing systems have traditionally been built using custom VLSI to meet real-time requirements. This leads to limited programmability and restricted flexibility. With recent technological advances in high performance computing, scalable systems based on heterogeneous "off the shelf" modules are attractive as computing platforms in real-time embedded environments, leading to an emerging class of Scalable Heterogeneous High Performance Embedded (SHHiPE) systems. These systems offer advantages of low-cost, scalability, easy programmability, software portability, and the ability to incorporate evolving hardware technology. In order to satisfy the timing and predictability requirements that arise in embedded environments, several issues must be considered. These issues arise at the hardware level-such as choice of processing element architecture, and also at the software level-issues related to operating system and communication libraries. We propose an integrated methodology to develop efficient parallel solutions for signal processing applications on the SHHiPE platforms. Our approach is to develop scalable portable algorithms based on accurate computational models of the hardware platforms. We present preliminary performance results of such an approach applied to a radar signal processing problem.
{"title":"Issues in using heterogeneous HPC systems for embedded real time signal processing applications","authors":"Prashanth B. Bhat, Y. Lim, V. Prasanna","doi":"10.1109/RTCSA.1995.528763","DOIUrl":"https://doi.org/10.1109/RTCSA.1995.528763","url":null,"abstract":"Embedded signal processing systems have traditionally been built using custom VLSI to meet real-time requirements. This leads to limited programmability and restricted flexibility. With recent technological advances in high performance computing, scalable systems based on heterogeneous \"off the shelf\" modules are attractive as computing platforms in real-time embedded environments, leading to an emerging class of Scalable Heterogeneous High Performance Embedded (SHHiPE) systems. These systems offer advantages of low-cost, scalability, easy programmability, software portability, and the ability to incorporate evolving hardware technology. In order to satisfy the timing and predictability requirements that arise in embedded environments, several issues must be considered. These issues arise at the hardware level-such as choice of processing element architecture, and also at the software level-issues related to operating system and communication libraries. We propose an integrated methodology to develop efficient parallel solutions for signal processing applications on the SHHiPE platforms. Our approach is to develop scalable portable algorithms based on accurate computational models of the hardware platforms. We present preliminary performance results of such an approach applied to a radar signal processing problem.","PeriodicalId":111365,"journal":{"name":"Proceedings Second International Workshop on Real-Time Computing Systems and Applications","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127936253","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 : 1995-10-25DOI: 10.1109/RTCSA.1995.528751
In-Guk Kim, Kyunghee Choi, Seung-Kyu Park, Dongyoon Kim, M. Hong
Distributed systems, where the processes send and receive their messages remotely, are generally based on the message communications. The execution of a process is blocked until the process receives a response from an other process for a requested message. In this paper, we propose two real-time scheduling methods for the tasks with blocking intervals. It is proven that every task set that is schedulable by Ming's method is also schedulable by one of the proposed methods. Also, the simulation shows that the schedulable ratios of task sets by the proposed methods are much higher than that obtained by Ming's method.
{"title":"Real-time scheduling of tasks that contain the external blocking intervals","authors":"In-Guk Kim, Kyunghee Choi, Seung-Kyu Park, Dongyoon Kim, M. Hong","doi":"10.1109/RTCSA.1995.528751","DOIUrl":"https://doi.org/10.1109/RTCSA.1995.528751","url":null,"abstract":"Distributed systems, where the processes send and receive their messages remotely, are generally based on the message communications. The execution of a process is blocked until the process receives a response from an other process for a requested message. In this paper, we propose two real-time scheduling methods for the tasks with blocking intervals. It is proven that every task set that is schedulable by Ming's method is also schedulable by one of the proposed methods. Also, the simulation shows that the schedulable ratios of task sets by the proposed methods are much higher than that obtained by Ming's method.","PeriodicalId":111365,"journal":{"name":"Proceedings Second International Workshop on Real-Time Computing Systems and Applications","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126485376","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 : 1995-10-25DOI: 10.1109/RTCSA.1995.528770
J. Katwijk, H. Toetenel
Teaching formal specification notations nowadays in regular software engineering courses presents more or less the same problems as teaching programming languages 15 years ago. Most software engineering students are practical. Issues of predicting code sizes from the size of the specification, issues of expressing problem complexity in terms of specification size are far more interesting for engineers than detailed semantic issues. Based on this observation, we are conducting a study to the proper use of formal specification notations in the process of software development. In this paper we discuss a number of notations in their use in the development of a simple case. The notations themselves are examined with regard to maturity, tool support, analyzability and executability.
{"title":"Comparing formal specifications by measuring","authors":"J. Katwijk, H. Toetenel","doi":"10.1109/RTCSA.1995.528770","DOIUrl":"https://doi.org/10.1109/RTCSA.1995.528770","url":null,"abstract":"Teaching formal specification notations nowadays in regular software engineering courses presents more or less the same problems as teaching programming languages 15 years ago. Most software engineering students are practical. Issues of predicting code sizes from the size of the specification, issues of expressing problem complexity in terms of specification size are far more interesting for engineers than detailed semantic issues. Based on this observation, we are conducting a study to the proper use of formal specification notations in the process of software development. In this paper we discuss a number of notations in their use in the development of a simple case. The notations themselves are examined with regard to maturity, tool support, analyzability and executability.","PeriodicalId":111365,"journal":{"name":"Proceedings Second International Workshop on Real-Time Computing Systems and Applications","volume":"750 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133016781","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 : 1995-10-25DOI: 10.1109/RTCSA.1995.528758
V. Lee, K. Lam, S. Hung
In recent years, the performance of distributed real-time database systems (DRTDBS) have been examined using different simulation models. In these models, the network issues are always being neglected. The networks are usually modeled as simple constant delay servers. However, it is found that the performance of the underlying network has significant impact on the overall performance of the DRTDBS. The results also showed that unpredictable behavior of the underlying network will give non-constant network transit time which in turn deter the overall system performance. To deal with this impact, different virtual deadline assignment schemes are proposed. The schemes assign a virtual deadline based on the current network condition to those transactions which require a comparatively better performance. Our results demonstrate that dynamically tuning the virtual deadlines of transactions depending on the condition of the network, yields a substantial improvement in the performance of that certain type of transactions without severely affecting the overall system performance.
{"title":"Virtual deadline assignment in distributed real-time database systems","authors":"V. Lee, K. Lam, S. Hung","doi":"10.1109/RTCSA.1995.528758","DOIUrl":"https://doi.org/10.1109/RTCSA.1995.528758","url":null,"abstract":"In recent years, the performance of distributed real-time database systems (DRTDBS) have been examined using different simulation models. In these models, the network issues are always being neglected. The networks are usually modeled as simple constant delay servers. However, it is found that the performance of the underlying network has significant impact on the overall performance of the DRTDBS. The results also showed that unpredictable behavior of the underlying network will give non-constant network transit time which in turn deter the overall system performance. To deal with this impact, different virtual deadline assignment schemes are proposed. The schemes assign a virtual deadline based on the current network condition to those transactions which require a comparatively better performance. Our results demonstrate that dynamically tuning the virtual deadlines of transactions depending on the condition of the network, yields a substantial improvement in the performance of that certain type of transactions without severely affecting the overall system performance.","PeriodicalId":111365,"journal":{"name":"Proceedings Second International Workshop on Real-Time Computing Systems and Applications","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131517215","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 : 1995-10-25DOI: 10.1109/RTCSA.1995.528746
T. Ogasawara
The predictability of the computation time of program modules is very important for estimating an accurate worst-case execution time (WCET) of a task in real-time systems. Dynamic storage allocation (DSA) is a common programming technique. Although many DSA algorithms have been developed, they focus on the average execution time rather than the WCET, making it is very difficult to calculate their WCET accurately. In this paper, we propose a new algorithm called Half-Fit whose WCET can be calculated accurately. The algorithm finds a free block without searching on a free list or tree, allowing extra unusable memory called incomplete memory use. In a simulation following a queueing model of M/G//spl infin/, Half-Fit has the advantage over the binary buddy system of more efficient storage utilization. The binary buddy system is a conventional algorithm whose WCET can be calculated.
{"title":"An algorithm with constant execution time for dynamic storage allocation","authors":"T. Ogasawara","doi":"10.1109/RTCSA.1995.528746","DOIUrl":"https://doi.org/10.1109/RTCSA.1995.528746","url":null,"abstract":"The predictability of the computation time of program modules is very important for estimating an accurate worst-case execution time (WCET) of a task in real-time systems. Dynamic storage allocation (DSA) is a common programming technique. Although many DSA algorithms have been developed, they focus on the average execution time rather than the WCET, making it is very difficult to calculate their WCET accurately. In this paper, we propose a new algorithm called Half-Fit whose WCET can be calculated accurately. The algorithm finds a free block without searching on a free list or tree, allowing extra unusable memory called incomplete memory use. In a simulation following a queueing model of M/G//spl infin/, Half-Fit has the advantage over the binary buddy system of more efficient storage utilization. The binary buddy system is a conventional algorithm whose WCET can be calculated.","PeriodicalId":111365,"journal":{"name":"Proceedings Second International Workshop on Real-Time Computing Systems and Applications","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126573751","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 : 1995-10-25DOI: 10.1109/RTCSA.1995.528743
J. Stankovic
Many real-time scheduling algorithms use simplistic sets of assumptions and this limits their applicability in practice. Often, a large real-time system has multiple scheduling algorithms and multi-level scheduling algorithms. Multiple algorithms arise when it is possible to partition the system into subsystems, each with their own algorithm. While this is a valuable approach, in this paper we focus on the issue of multi-level scheduling. Multi-level scheduling arises for various important reasons. In this invited presentation we discuss multi-level scheduling examples from a process/thread model, local/distributed scheduling, manufacturing, and multimedia.
{"title":"The many faces of multi-level real-time scheduling","authors":"J. Stankovic","doi":"10.1109/RTCSA.1995.528743","DOIUrl":"https://doi.org/10.1109/RTCSA.1995.528743","url":null,"abstract":"Many real-time scheduling algorithms use simplistic sets of assumptions and this limits their applicability in practice. Often, a large real-time system has multiple scheduling algorithms and multi-level scheduling algorithms. Multiple algorithms arise when it is possible to partition the system into subsystems, each with their own algorithm. While this is a valuable approach, in this paper we focus on the issue of multi-level scheduling. Multi-level scheduling arises for various important reasons. In this invited presentation we discuss multi-level scheduling examples from a process/thread model, local/distributed scheduling, manufacturing, and multimedia.","PeriodicalId":111365,"journal":{"name":"Proceedings Second International Workshop on Real-Time Computing Systems and Applications","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115903907","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 : 1995-10-25DOI: 10.1109/RTCSA.1995.528745
O. Hammami
This paper makes a contribution to real time aspects of cache systems by proposing a new cache organization with the potential of reducing hit time and increasing hit ratio. Although, predictability remains a concern, a better potential can be found with these caches due to a total elimination of conflict misses. This proposal simply constitutes a starting point for further studies.
{"title":"Real time aspects of cluster based caches","authors":"O. Hammami","doi":"10.1109/RTCSA.1995.528745","DOIUrl":"https://doi.org/10.1109/RTCSA.1995.528745","url":null,"abstract":"This paper makes a contribution to real time aspects of cache systems by proposing a new cache organization with the potential of reducing hit time and increasing hit ratio. Although, predictability remains a concern, a better potential can be found with these caches due to a total elimination of conflict misses. This proposal simply constitutes a starting point for further studies.","PeriodicalId":111365,"journal":{"name":"Proceedings Second International Workshop on Real-Time Computing Systems and Applications","volume":"306 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116607421","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 : 1995-10-25DOI: 10.1109/RTCSA.1995.528774
Sheng-Tzong Cheng, A. Agrawala
Allocation problem has always been one of the fundamental issues of building the applications in real-time computing systems. For real-time applications, the allocation problem should directly address the issues of task and communication scheduling. In this context, the allocation of tasks has to fully utilize the available processors and the scheduling of tasks has to meet the specified timing constraints. Clearly, the execution of tasks under the allocation and schedule has to satisfy the precedence, resources, and other synchronization constraints among them. Recently, the timing requirements of the real-time systems emerge that the relative timing constraints are imposed on the consecutive executions of each task and the inter-task temporal relationships are specified across task periods. In this paper we consider the allocation and scheduling problem of the periodic tasks with such timing requirements. Given a set of periodic tasks, we consider the least common multiple (LCM) of the task periods. Each task is extended to several instances within the LCM. The scheduling window for each task instance is derived to satisfy the timing constraints. We develop a simulated annealing algorithm as the overall control algorithm. An example problem of the sanitized version of the Boeing 777 Aircraft Information Management System is solved by the algorithm. Experimental results show that the algorithm solves the problem in a reasonable time complexity.
{"title":"Allocation and scheduling of real-time periodic tasks with relative timing constraints","authors":"Sheng-Tzong Cheng, A. Agrawala","doi":"10.1109/RTCSA.1995.528774","DOIUrl":"https://doi.org/10.1109/RTCSA.1995.528774","url":null,"abstract":"Allocation problem has always been one of the fundamental issues of building the applications in real-time computing systems. For real-time applications, the allocation problem should directly address the issues of task and communication scheduling. In this context, the allocation of tasks has to fully utilize the available processors and the scheduling of tasks has to meet the specified timing constraints. Clearly, the execution of tasks under the allocation and schedule has to satisfy the precedence, resources, and other synchronization constraints among them. Recently, the timing requirements of the real-time systems emerge that the relative timing constraints are imposed on the consecutive executions of each task and the inter-task temporal relationships are specified across task periods. In this paper we consider the allocation and scheduling problem of the periodic tasks with such timing requirements. Given a set of periodic tasks, we consider the least common multiple (LCM) of the task periods. Each task is extended to several instances within the LCM. The scheduling window for each task instance is derived to satisfy the timing constraints. We develop a simulated annealing algorithm as the overall control algorithm. An example problem of the sanitized version of the Boeing 777 Aircraft Information Management System is solved by the algorithm. Experimental results show that the algorithm solves the problem in a reasonable time complexity.","PeriodicalId":111365,"journal":{"name":"Proceedings Second International Workshop on Real-Time Computing Systems and Applications","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115665777","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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