To Örebro University

In this paper, we propose a new protocol for handling resource sharing among prioritized real-time applications composed on a multiprocessor platform. We propose an optimal priority assignment algorithm which assigns unique priorities to the applications based on information in their interfaces. We have performed experimental evaluations to compare the proposed protocol (called MSOS-Priority) to the current state of the art locking protocols under multiprocessor partitioned scheduling, i.e., MPCP, MSRP, FMLP, MSOS, and OMLP. The valuations show that MSOS-Priority mostly performs significantly better than alternative approaches.

In this paper we propose a general synchronization protocol for resource sharing among independently-developed real-time applications (components) on multi-core platforms. This protocol is a generalization of a previously proposed synchronization protocol (MSOS). In our proposed protocol, each component is statically allocated on a dedicated subset of processors (called cluster). A component has its own internal scheduler by which its tasks are scheduled. In this paper we focus on multiprocessor global fixed-priority preemptive scheduling algorithms to be used to schedule the tasks inside each component. Sharing the local resources is handled by the Priority Inheritance Protocol (PIP). For sharing the global resources (inter-component resource sharing) we have studied usage of FIFO and Round-Robin queues for access the resources across the components and usage of FIFO and prioritized queues inside the components. We have derived schedulability analysis for the different queue handling alternatives and compared their performance by using experimental evaluations. Finally, we have shown that the integration phase can be formulated in the form of a nonlinear integer programming problem where solution techniques in this domain can be used to minimize the total number of processors required to guarantee the schedulability of all components. As a proof of concept we have only provided the formulation for FIFO queues.

MSOS (Multiprocessors Synchronization protocol for real-time Open Systems) is a synchronization protocol for handling resource sharing among independently-developed realtime applications (components) on multi-core platforms. MSOS does not consider any priority setting among applications. To handle resource sharing based on the priority of applications, in this paper we propose a new protocol that allows for resource sharing among prioritized real-time applications on a multi-core platform. We propose an optimal priority assignment algorithm which assigns unique priorities to the applications based on information in their interfaces. We have performed experimental evaluations to compare the proposed protocol (called MSOS-Priority) to the existing MSOS as well as to the current state of the art locking protocols under multiprocessor partitioned scheduling, i.e., MPCP, MSRP, FMLP and OMLP. The evaluations show that MSOS-Priority mostly performs significantly better than alternative approaches.

Semi-partitioned scheduling has become the subject of recent interest for multiprocessors due to better utilization results, compared to conventional global and partitioned scheduling algorithms. Under semi-partitioned scheduling, a major group of tasks are assigned to fixed processors while a low number of tasks are allocated to more than one processor. Various task assigning techniques have recently been proposed in a semi-partitioned environment. However, a synchronization mechanism for resource sharing among tasks in semi-partitioned scheduling has not yet been investigated. In this paper we propose and evaluate two methods for handling resource sharing under semi-partitioned scheduling in multiprocessor platforms. The main challenge addressed in this paper is to serve the resource requests of tasks that are assigned to different processors.

Semi-partitioned scheduling has been the subject of recent interest, compared with conventional global and partitioned scheduling algorithms for multiprocessors, due to better utilization results. In semi-partitioned scheduling most tasks are assigned to fixed processors while a low number of tasks are split up and allocated to different processors. Various techniques have recently been proposed to assign tasks in a semi-partitioned environment. However, an appropriate resource sharing mechanism for handling the resource requests between tasks in semi-partitioned scheduling has not yet been investigated. In this paper we propose two methods for handling resource sharing under semi-partitioned scheduling in multiprocessor platforms. The main challenge is to handle the resource requests of tasks that are split over multiple processors.

In this paper we propose a synchronization protocol for resource sharing among independently-developed real-time systems on multi-coreplatforms. The systems may use different scheduling policies and they may have their own local priority settings. Each system is allocated on a dedicated processor (core). In the proposed synchronization protocol, each system is abstracted by an interface which abstracts the information needed for supporting global resources. The protocol facilitates the composability of various real-time systems with different scheduling and priority settings on a multi-core platform. We have performed experimental evaluations and compared the performance of our proposed protocol (MSOS) against the two existing synchronization protocols MPCP and FMLP. The results show that the new synchronization protocol enables composability without any significant loss of performance. In fact, in most cases the new protocol performs better than at least one of the other two synchronization protocols. Hence, we believe that the proposed protocol is a viable solution for synchronization among independently-developedreal-time systems executing on a multi-core platform.

Recently there has been a lot of interest in coexisting of multiple independently-developed real-time applications on a shared open platform. On the other hand, emerging of multi-core platforms and the performance and possibilities they offer has attracted a lot of attention in multiprocessor real-time analysis, protocols and techniques. Co-executing independently- developedreal-time applications on a shared multiprocessor system, where each application executes on a dedicated sub set of processors, requires to overcome the problem of handling mutually exclusive shared resources among those applications. To handle resource sharing, it is important to determine the Resource Hold Time (RHT), i.e., the maximum duration of time that an application locks a shared resource.

In this paper, we study resource hold times under multiprocessor static-priority global scheduling. We present how to compute RHT's for each resource in an application. We also show how to decrease the RHT's without compromising the schedulability of the application. We show that decreasing all RHT's for all shared resources is a multiobjective optimization problem and there can exist multiple Paretooptimal solutions.

In this paper we propose a synchronization protocol for resource sharing among independently-developed real-time systems on multi-core platforms. The systems may use different scheduling policies and they may have arbitrary priority settings. When using this synchronization protocol each processor is abstracted by an interface which consists of a set of requirements. A requirement depends only on the worst-case time the processor may wait for resources, i.e., the maximum number of times that the resources can be blocked by other processors. We have derived schedulability conditions for each processor and based on the analysis we extract the interface of the processor. In this paper, we focus on the cases when each system is allocated on a dedicated processor.

Supporting resource sharing in multiprocessor architectures is one of the problems which may limit the benefits that can be archived using this type of architecture. Many approaches and algorithms have been proposed to support resource sharing, however, most of them impose either high blocking times on tasks or require a large memory size. In this paper we investigate the possibility of combining the lock-based approaches and wait-free approaches (using multiple buffers) in order to decrease both the blocking time that may affect the schedulability of tasks and the required memory. To achieve this, we propose a solution based on evaluating the maximum allowed blocking time on each task according to the schedulability analysis, and then find the minimum memory requirement for each resource such that it limits the blocking times on tasks to be less than the maximum allowed blocking times.

In this paper we propose a message passing synchronization protocol for resource sharing among real-time applications on multi-core platforms where each application is allocated on a cluster of cores. In this protocol the resources that are only used within an application (local resources) are handled by shared memory synchronization while the resources shared cross applications (global resources) are accessed by means of message passing. In our protocol the global resources are safely accessed without requiring to lock the resources explicitly. The goal is to avoid resource locking using shared memory, since accessing shared memory in multi-cores is very time consuming, whereas message passing has the potential to be much more efficient in systems with deep memory hierarchies.