S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proc. 32nd IEEE Symp. on the Foundations of Computer Science, pages 101-- 110, 1991.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... whenever there exists a schedule meeting the deadlines of all jobs released, EDF can always do so [8] However, when the system is possibly overloaded, no algorithm has a worst case performance guarantee in the sense that the performance cannot match or be competitive against the o ine adversary [2]. In recent years, a plausible approach to achieving better performance guarantee for online scheduling (without restricting the inputs) is to allow the online scheduler to use a faster processor than the o ine adversary (e.g. 3, 5, 6, 9, 12,16, 18] Intuitively, we use a faster processor to ....

....algorithm. Previous work: The early work of Dertouzos [8] showed that for underloaded systems, the Earliest Deadline First (EDF) strategy is 1 competitive. But in general, no O(1) competitive rm deadline scheduler exists; indeed, the best possible competitive ratio is (1 (Baruah et al. [2], Koren and Shasha [15] To obtain better performance guarantees, one can allow online schedulers to use a faster processor. Speci cally, one compares an online scheduler that is given a faster processor but has no knowledge about the future against an o ine scheduler that uses only a unit speed ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the 32th Annual Symposium on Foundations of Computer Science, pages 101-110, 1991.

....deadlines is no easier than the general problem. In fact, the best lower bound results on rm deadline scheduling are based on the tight deadline setting. Even with the tight deadline assumption, no on line algorithm (using a processor of ordinary speed) can be 1 competitive and Baruah et al. [2, 1] actually showed that no algorithm can achieve a competitive ratio less than ( Note that when k = 1, 4. If deadlines are known to be not tight, only a weaker lower bound has been known DasGupta and Palis [5] showed that if all jobs have a stretch factor 1 , then no ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the IEEE Thirty-second Annual Symposium on the Foundations of Computer Science, pages 101-110, 1991.

.... whenever there exists a schedule meeting the deadlines of all jobs released, EDF can always do so [6] However, when the system is possibly overloaded, no algorithm has a worst case performance guarantee in the sense that the performance cannot match or be competitive against the o#ine adversary [2]. In recent years, a plausible approach to studying better performance guarantee for online scheduling (without restricting the inputs) is to allow the online scheduler to use a faster processor than the o#ine adversary [3,5,7,10,14,16] Intuitively, we need a faster processor to compensate the ....

....Dertouzos [6] showed that for underloaded systems, the Earliest Deadline First (EDF) strategy is optimal. But in general, no optimal or O(1) competitive firm deadline scheduler can exist; indeed, the best competitive ratio has a matching upper bound and lower bound of (1 # k) Baruah et al. [2], Koren and Shasha [13] To obtain better performance guarantee, we allow online schedulers to use a faster processor. Specifically, we compare an online scheduler that is given a faster processor but has no knowledge about the future against an o#ine scheduler that uses only a unit speed ....

[Article contains additional citation context not shown here]

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proc. 32th FOCS, pages 101--110, 1991.

....when the system is overloaded or involves more than one processor, edf has no performance guarantee in the sense that its performance cannot match or even be competitive against the optimal o line algorithm. Indeed, in most settings, no online algorithm has this sort of performance guarantee [2, 8]. In recent years, a plausible approach to studying performance guarantee for online scheduling without restricting the inputs is to allow the online scheduler to use faster processors [1, 3, 5, 9, 10, 13, 14] Intuitively, we want to study how e ective faster processors can compensate the online ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the 1991.

.... whenever there exists a schedule meeting the deadlines of all jobs released, EDF can always do so [7] However, when the system is possibly overloaded, no algorithm has a worst case performance guarantee in the sense that the performance cannot match or be competitive against the o ine adversary [2]. In recent years, a plausible approach to studying better performance guarantee for online scheduling (without restricting the inputs) is to allow the online scheduler to use a faster processor than the o ine adversary [3, 5, 8, 11, 15, 17] Intuitively, we use a faster processor to compensate ....

....[7] showed that for underloaded systems, the Earliest Deadline First (EDF) strategy is optimal. But in general, no optimal or O(1) competitive rm deadline scheduler can be constructed; indeed, the best competitive ratio has a matching upper bound and lower bound of (1 (Baruah et al. [2], Koren and Shasha [14] To obtain better performance guarantee, we allow online schedulers to use a faster processor. Speci cally, we compare an online scheduler that is given a faster processor but has no knowledge about the future against an o ine scheduler that uses only a unit speed ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the 32th Annual Symposium on Foundations of Computer Science, pages 101-110, 1991.

....of all jobs released, EDF can always do so [5] However, without the underloaded assumption, no on line algorithm can be optimal regarding processor utilization, i.e. no algorithm can match the optimal offline algorithm on the total work of jobs meeting the deadlines. Indeed, Baruah et al. [1, 2] showed that there is no on line algorithm that can guarantee to attain more than one fourth of the processor utilization of the optimal offline algorithm. Another way to express this result is that the competitive ratio of any on line algorithm is at least 4. This lower bound is tight as matching ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the IEEE 32nd Annual Symposium on Foundations of Computer Science, pages 101--110, San Juan, Puerto Rico, 1991.

....with tight deadlines is no easier than the general problem. In fact, the best lower bound results on rm deadline scheduling are based on the tight deadline setting. Even with the tight deadline assumption, no on line algorithm (using a processor of ordinary speed) can be optimal and Baruah et al. [2, 1] actually showed that no algorithm can achieve a competitive ratio less than ( Note that when k = 1, 4. If deadlines are known to be not tight, only a weaker lower bound has been known DasGupta and Palis [4] showed that if all jobs have a stretch factor 1 , then no algorithm ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the IEEE Thirtysecond Annual Symposium on the Foundations of Computer Science, pages 101{ 110, San Juan, Porto Rico, October 1991.

....not match our requirements because of their sharp decrease. As a result of the rm deadline, the real time scheduling model is hard to approximate. The optimal deterministic competitive ratio for the uniprocessor case is ( where is the ratio between the maximum and minimum bene t densities [3, 4, 7]. For the special case where = 1, there is a 4 competitive algorithm. The optimal randomized competitive ratio for the uniprocessor case is O(min(log ; log ) where is the ratio between the longest and shortest job [6] For the multiprocessor case, Koren and Shasha [8] showed that when the ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In 32nd IEEE Annual Symposium on Foundations of Computer Science, pages 100-110, San Juan, Puerto Rico, 1991.

....count (CC) Informally, EPU measures the fraction of time during overload that the processor spends on executing tasks that will complete by their deadlines, while CC measures the number of tasks executed to completion during the overload interval. To the best of our knowledge, previous work [2, 14, 3, 9, 15] focused on the case when EPU is the measure of scheduling performance. Some algorithms have also been proposed to deal with overloads that improve the performance of EDF that is optimal when system is underloaded [2, 8, 11] Baruah et al. 13] have shown that there exists an upper bound on the ....

S. K. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, D. Shasha. On-line scheduling in the presence of overload. In Proceedings of 32nd Ann. IEEE Symp. Foundations of Computer Science, Octorber 1991.

.... k server and generic task system problems [23, 21, 5] While the single request sequence model captures many important problems, there are many others which do not fall into this category, such as some operating system scheduling problems [18, 12, 13, 24] and some real time scheduling problems [20, 4, 11]. In a typical problem, there is a single system resource such as a processor and, at any given time, there are multiple requests in the system waiting to be serviced. As a result, the underlying problem is deciding which current request should the system service rather than which system resource ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proc. 32nd IEEE Symp. on the Foundations of Computer Science, pages 101-110, 1991.

....which is 1=k of the capacity of the link for some integer k. Even for this restricted model we show that any deterministic on line algorithm has a competitive ratio of at most 0:66 (the bound holds for all k) Our model is closely related to on line preemptive task scheduling under overload [7, 6, 13, 14, 19, 18]. Our impossibility result applies to this problem as well. Our work extends previous work of Garay and Gopal [11] and Garay et al. 12] These papers also consider on line bandwidth allocation with preemption on networks with line topology. However, they greatly simplify the model by assuming ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proc. 32nd IEEE Symp. on Foundations of Computer Science, pages 101--110, 1991.

No context found.

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha, "On-Line Scheduling in the Presence of Overload," Proc. 32nd Ann. IEEE Symp. Foundations of Computer Science, San Juan, Puerto Rico, Oct. 1991.

....we will use Some very interesting and important results in real time multiprocessor scheduling theory were obtained in the mid 1990 s. We will make use of two of these results in this paper; these two results are briefly described below. Resource augmentation. It has previously been shown [7, 6, 5] that on line real time scheduling algorithms tend to perform extremely poorly under overloaded conditions. Phillips, Stein, Torng, and Wein [19] explored the use of resource augmentation techniques for the on line scheduling of real time jobs 2 ; the goal was to determine whether an on line ....

.... the use of resource augmentation techniques for the on line scheduling of real time jobs 2 ; the goal was to determine whether an on line algorithm, if provided with faster processors than those available to a clairvoyant algorithm, could perform better than is implied by the bounds derived in [7, 6, 5]. Although we are not studying on line scheduling in this paper all the parameters of all the periodic tasks are assumed a priori known it nevertheless turns out that a particular result from [19] will prove very useful to us in our study of static priority multiprocessor scheduling. We ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proc. of the 32nd Annual IEEE Symposium on Foundations of Computer Science, pages 100--110, San Juan, Puerto Rico, Oct. 1991.

.... real time tasks, several on line scheduling algorithms have been designed [1, 2] that are optimal under non overloaded conditions# however, it is known that no on line scheduling algorithm can guarantee to avoid a drastic fall in performance vis a vis offline algorithms upon the onset of overload [3,4, 5]. A natural approachtowards overcoming this performance degradation upon overload would be bymoving from a uniprocessor to a multi processor platform# unfortunately, such an approach brings with it a host of new problems, arising from the twin facts that (i) multiprocessor scheduling is much more ....

....[2] are optimal in the sense that they have a competitive factor of one, irrespective of the metric chosen. When a uniprocessor system becomes overloaded, however, it is known that on line algorithms can perform poorly as compared to their clairvoyantcounterparts. In particular, it has been shown[3,4]thatwithrespecttotheuniform density metric in whichavalue of T:e is obtained for completing task T by its deadline no on line scheduling algorithm can haveacompetitive factor greater than 1=4. With respect to the uniform value metric in whichavalue of 1 is obtained for completing task ....

[Article contains additional citation context not shown here]

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the 32nd Annual IEEE Symposium on Foundations of Computer Science, pages 100--110, San Juan, Puerto Rico, October 1991. IEEE Computer Society Press.

....if it is 1 competitive. The off line scheduling problem with respect to EPU given a set of tasks, determine a schedule that maximizes the EPU is easily seen to be NP hard (transformation from bin packing) On line scheduling to maximize EPU is also quite well understood (see, for example, [2,1]) It is known that no on line scheduling algorithm can be more than 4 competitive with respect to this metric# furthermore, this bound is tightinthat4competitivescheduling algorithms for this problem have been designed. Scheduling to maximize completion count has been rather less studied. From ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the 32nd Annual IEEE Symposium on Foundations of Computer Science, pages 100--110, San Juan, Puerto Rico, October 1991. IEEE Computer Society Press.

.... begun investigating the impact of overload with respect to CC, and an initial set 2 0 0 1 4 10 3 8 TASK T1 TASK T2 time Figure 1: Effective Processor Utilization (EPU) EPU metric has been widely used in the analysis of real time scheduling algorithms under conditions of overload (e.g. [15, 4, 3, 13, 17]) A detailed discussion of the applicability of this metric to real time systems is provided in [15] In particular, our goal is to compare the EPU performance of on line scheduling algorithms against that of an optimal off line (or clairvoyant) algorithm. On line schedulers make scheduling ....

....larger execution times, since they contribute more to the EPU. The ROBUST Scheduler. The optimality results in [7] ensure that Earliest Deadline First schedulers, which execute tasks in deadline order, guarantee an EPU of 1.0 under normal (non overload) conditions. Furthermore, it has been shown [4, 3] that no uniprocessor on line scheduling algorithm can guarantee an EPU greater than 0:25 under overload (this bound is tight) Taken in conjunction, these results imply that the onset of an emergency may, in of results for this metric are presented in [2] 3 general, force a deterioration in ....

[Article contains additional citation context not shown here]

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proc. of the 32nd Annual IEEE Symposium on Foundations of Computer Science, San Juan, Puerto Rico, October 1991. IEEE Computer Society Press.

....are best modeled by modifications to these measures, or perhaps even some combination of them. Performance Results. With respect to the EPU metric, it has been proved that no uniprocessor on line scheduling algorithm can guarantee an EPU greater than 25 percent under conditions of overload [3, 2]. This bound has also been shown to be tight [2, 8] These results hold in the general case, when the deadlines of the input tasks may be arbitrarily tight or stringent. Recently, the effect on EPU in environments where there is a limit on the stringency of task deadlines has been studied [1] ....

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the 32nd Annual IEEE Symposium on Foundations of Computer Science, San Juan, Puerto Rico, October 1991. IEEE Computer Society Press.

No context found.

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proc. 32nd IEEE Symp. on the Foundations of Computer Science, pages 101-- 110, 1991.

No context found.

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proc. 32nd IEEE Symp. on the Foundations of Computer Science, pages 101-110, 1991.

No context found.

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the 32nd IEEE Symposium on the Foundations of Computer Science, pages 101-110, 1991.

No context found.

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha, "On-Line Scheduling in the Presence of Overload," Proc. IEEE Ann. Symp. Foundations of Computer Science, pp. 101-110, 1991.

No context found.

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier and D. Shasha "On-line Scheduling in the Presence of Overload," in IEEE Symposium on Foundations of Computer Science(FOCS), pp.100-110, 1991

No context found.

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the 32th Annual Symposium on Foundations of Computer Science, pages 101-110, 1991.

No context found.

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proceedings of the 1991.

No context found.

S. Baruah, G. Koren, B. Mishra, A. Raghunathan, L. Rosier, and D. Shasha. On-line scheduling in the presence of overload. In Proc. 1991.

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