M. Caccamo and L. Sha. Aperiodic servers with resource constraints. In IEEE Real-Time Systems Symposium, London, England, December 2001.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....servers. We also discuss several inheritance based protocols as possible alternatives. Work supported by NSF grants CCR 9972211, CCR 9988327, and ITR 0082866. 1 Introduction In recent years, there has been considerable interest in fair scheduling algorithms for multiprocessor systems [3, 4, 5, 7, 8, 9, 16, 23]. Under fair disciplines, each task is assigned a weight that represents its share of the system s resources. At present, fair scheduling algorithms are the only known means for optimally scheduling recurrent real time tasks on multiprocessors, and thus are of importance from a theoretical ....

....implemented using non fair scheduling algorithms (or both) and thus cannot be directly applied in fair scheduled multiprocessor systems. Indeed, synchronization issues in fair scheduled uniprocessor systems and related bandwidth preserving server schemes were first considered only very recently [10, 11, 14, 16]. In recent work [13] we demonstrated the effectiveness of lock free algorithms for implementing shared objects in fair scheduled systems. Lock free algorithms do not use semaphores to synchronize tasks. Hence, tasks never block. Blocking can be particularly problematic in fair scheduled ....

M. Caccamo and L. Sha. Aperiodic servers with resource constraints. In Proceedings of the 22nd IEEE Real-Time Systems Symposium, pages 161--170. December 2001.

....to guarantee schedulability of periodic tasks using the priority ceiling protocols by the rate monotonic algorithm. Work by Ghazalie and Baker [7] take into account resource constraints in developing a schedulability test using Liu and Layland s utilization bound. Other approaches [4] 10] and [5] extend the work for aperiodic servers. The approach in this paper incorporates the effects of blocking during derivation of the aperiodic utilization bound, thus enabling derivation of bounds parameterized by a term dependent on the blocking effects. Interestingly, the resulting term is under a ....

M. Caccamo and L. Sha. Aperiodic servers with resource constraints. In IEEE Real-Time Systems Symposium, London, England, December 2001.

.... rates prevents misbehaving tasks from exceeding their weight defined rates (temporal isolation) and allows real time deadlines to be guaranteed, where feasible (timeliness) In recent years, there has been considerable interest in fair scheduling algorithms for multiprocessor systems [3, 4, 5, 7, 8, 9, 16]. One reason for this interest is the fact that fair scheduling algorithms, at present, are the only known means for optimally scheduling recurrent real time tasks on multiprocessors. In addition, there has been growing practical interest in such algorithms. Ensim Corp. for example, an Internet ....

....synchronization has been directed at uniprocessor systems, or systems implemented using non fair scheduling algorithms (or both) and thus cannot be directly applied in fair scheduled multiprocessor systems. Indeed, fair scheduled uniprocessor systems were first considered only very recently [10, 11, 14, 16]. In this paper, we consider the problem of object sharing in fair scheduled multiprocessor systems. We primarily focus on the use of lock free objects, which are implemented without critical sections or related mechanisms. However, some lock based alternatives are briefly considered as well. We ....

M. Caccamo and L. Sha. Aperiodic servers with resource constraints. In Proceedings of the 22nd IEEE Real-Time Systems Symposium, pages 161--170. December 2001.

....similar to Priority Ceiling, the Stack Resource Policy, was presented by Baker in [3] In [10] it is shown how to combine the SRP algorithm with aperiodic servers, in order to share resources between aperiodic tasks and hard real time tasks. This approach has been recently applied to the CBS in [6]. However, this kind of solutions require an apriori knowledge of the maximum resource usage time for each task, and in an open system it is impossible to have such an a priori knowledge. For this reason, resource sharing protocols such as PI, PC, or SRP cannot be directly used in an Open System. ....

....obtain: n X i=1 C i I i T i 1 which may lead to a lower utilization with respect to Equation (1) because all the blocking times are summed together. Hence, if we are dealing with a hard real time system, it is probably better to use other scheduling strategies like the one presented in [6]. However, algorithm BWI is more suitable for Open Systems where hard, soft and non real time applications can coexist and it is impossible to perform an o line analysis for the entire system. Of course, this comes at a cost of a lower utilization for hard real time tasks. 6. Interference Time ....

M. Caccamo and L. Sha. Aperiodic servers with resource constraints. In Proceedings of the IEEE RealTime Systems Symposium, London. UK, December 2001.

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M. Caccamo and L. Sha. Aperiodic servers with resource constraints. In IEEE Real-Time Systems Symposium, London, England, December 2001.

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