DPCP-p: A Distributed Locking Protocol for Parallel Real-Time Tasks

TL;DR

This paper introduces an extension of the Distributed Priority Ceiling Protocol for parallel real-time tasks, providing a distributed locking framework that improves schedulability and response time bounds on multi-core systems.

Contribution

It extends DPCP for federated scheduling of parallel tasks, with new heuristics and analysis techniques for task and resource partitioning.

Findings

Significant schedulability improvements over existing protocols.

Effective bounding of task response times.

Validated performance on multi-core processors with heavy tasks.

Abstract

Real-time scheduling and locking protocols are fundamental facilities to construct time-critical systems. For parallel real-time tasks, predictable locking protocols are required when concurrent sub-jobs mutually exclusive access to shared resources. This paper for the first time studies the distributed synchronization framework of parallel real-time tasks, where both tasks and global resources are partitioned to designated processors, and requests to each global resource are conducted on the processor on which the resource is partitioned. We extend the Distributed Priority Ceiling Protocol (DPCP) for parallel tasks under federated scheduling, with which we proved that a request can be blocked by at most one lower-priority request. We develop task and resource partitioning heuristics and propose analysis techniques to safely bound the task response times. Numerical evaluation (with heavy tasks on 8-, 16-, and 32-core processors) indicates that the proposed methods improve the schedulability significantly compared to the state-of-the-art locking protocols under federated scheduling.