Simultaneous Multithreading and Hard Real Time: Can It Be Safe?

Sims Hill Osborne, James H. Anderson

The applicability of Simultaneous Multithreading (SMT) to real-time systems has been hampered by the difficulty of obtaining reliable execution costs in an SMT-enabled system. This problem is addressed by introducing a scheduling framework, called CERT-MT, that combines scheduling-aware timing analysis with a cyclic-executive scheduler in a way that minimizes SMT-related timing variations. The proposed scheduling-aware timing analysis is based on maximum observed execution times and accounts for the uncertainty inherent in measurement-based timing analysis. The timing analysis is found to work for tasks with and without SMT, though some adjustments are required in the former case. A large-scale schedulability study is presented that shows CERT-MT can schedule systems with total utilizations approaching 1.4 times the core count, without sacrificing safety.

The paper will be presented in the session
Hardware II  SMT, tracing and more coherence – Thursday, July 9, 14:30 – 15:10 (CET) and 15:50 – 16:50 (CET)


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