New Schedulability Analysis for MrsP

In this paper we consider a spin-based multiprocessor locking protocol, named the Multiprocessor resource sharing Protocol (MrsP). MrsP adopts a helping-mechanism where the preempted resource holder can migrate. The original schedulability analysis of MrsP carries considerable pessimism as it has been developed assuming limited knowledge of the resource usage for each remote task. In this paper new MrsP schedulability analysis is developed that takes into account such knowledge to provide a less pessimistic analysis than that of the original analysis. Our experiments show that, theoretically, the new analysis offers better (at least identical) schedulability than the FIFO non-preemptive protocol, and can outperform FIFO preemptive spin locks under systems with either intensive resource contention or long critical sections. The paper also develops analysis to include the overhead of MrsP’s helping mechanism. Although MrsP’s helping mechanism theoretically increases schedulability, our evaluation shows that this increase may be negated when the overheads of migrations are taken into account. To mitigate this, we have modified the MrsP protocol to introduce a short non-preemptive section following migration. Our experiments demonstrate that with migration cost, MrsP may not be favourable for short critical sections but provides a better schedulability than other FIFO spin-based protocols when long critical sections are applied

A FIFO Spin-based Resource Control Framework for Symmetric Multiprocessing

Managing shared resources in multiprocessor real-time systems can often lead to considerable schedulability sacrifice, and currently there exist no optimal multiprocessor resource sharing solutions. In addition, the choice of task mapping and priority ordering algorithms also has a direct impact on the efficiency of multiprocessor resource sharing. This thesis argues that instead of adopting a single resource sharing protocol with the traditional task mapping (e.g., the task allocation schemes that are based on utilisation only) and priority ordering (e.g., the Deadline Monotonic Priority Ordering) algorithms, the schedulability loss for managing shared resources on multiprocessors can be effectively reduced by applying a combination of appropriately chosen resource sharing protocols with new resource-oriented task allocation schemes and a new search-based priority ordering algorithm (which are independent from multiprocessor resource sharing protocols and the corresponding schedulability tests). In this thesis, a Flexible Multiprocessor Resource Sharing (FMRS) framework is proposed that aims to provide feasible resource sharing, task allocation and priority assignment solutions to fully-partitioned systems with shared resources, where each resource is controlled by a designated locking protocol. To achieve this, the candidate resource sharing protocols for this framework are firstly determined with a new schedulability test developed to support the analysis of systems with multiple locking protocols in use. Then, besides the existing algorithms, three new resource-orientated task allocation schemes and a search-based priority ordering algorithm are developed for the FMRS framework as the task mapping and priority ordering solutions. The choices of which locking protocols, task allocation and priority ordering algorithm should be adopted to a given system are determined off-line via a genetic algorithm. As demonstrated by evaluations, the FMRS framework can facilitate multiprocessor resource sharing and has a better performance than the traditional resource control and task scheduling techniques for fully-partitioned systems

Supporting Nested Resources in MrsP

The original MrsP proposal presented a new multiprocessor resource sharing protocol based on the properties and behaviour of the Priority Ceiling Protocol, supported by a novel helping mechanism. While this approach proved to be as simple and elegant as the single processor protocol, the implications with regard to nested resources was identified as requiring further clarification. In this work we present a complete approach to nested resources behaviour and analysis for the MrsP protocol

Investigating the Correctness and Efficiency of MrsP in Fully Partitioned Systems

MrsP is a FIFO spin-based protocol that adopts a helping mechanism, where a resource holder can migrate to a remote processor to keep executing if it is preempted. In practice, allowing resource-holding tasks to migrate can raise implementation issues and run-time corner cases. In this paper, we present an investigation of the correctness and efficiency of implementing MrsP in fully partitioned systems. We identify potential race conditions and corner cases of the protocol due to the use of migrations. Then, new facilities are proposed to pre- vent the issues and to provide more efficient resource-accessing behaviours. Finally, evaluations are performed to demonstrate the impact of the run-time issues and to testify the effect of proposed facilities