Soft Error Reliability Using Virtual Platforms by Felipe Rocha da Rosa & Luciano Ost & Ricardo Reis

Author:Felipe Rocha da Rosa & Luciano Ost & Ricardo Reis
Language: eng
Format: epub
ISBN: 9783030557041
Publisher: Springer International Publishing

4.2.2 Instruction-Accurate Simulation Engine Parameters Impact on Soft Error Assessment

The previous subsection explored the soft error analysis accuracy of the OVPsim-FIM instruction-accurate framework against cycle-accurate gem5. Results show an average error of 11% in all cases (considering the gem5 atomic), with the worst case achieving up to 40%. Especially, the OpenMP applications displayed a more significant mismatch than the MPI or serial ones. This subsection investigates the origin of such mismatch and analyzes some solutions to improve the OVPsim-FIM accuracy. First, it is necessary to understand how the gem5 and OVPsim software simulation approaches behave under fault presence. The gem5 describes the target microarchitecture as components (i.e., register file, pipeline, cache) interconnected by a series of events. A scheduler in the gem5 engine executes these events at each simulation tick, updating the whole system state including multiple cores, memories, and other subsystems. Events are executed at a rate of 500 ticks per CPU cycle in the simulated system, and consequently, a complete instruction takes a couple of thousands of ticks.

The OVPsim relies on just-in-time (JIT) dynamic instruction translation engine, which translates the target ISA (e.g., ARMv7, ARMv8) to host ×86-64 instructions, providing its higher simulation speed. Further, a complete instruction is the OVPsim minimal simulation granularity, in other words, the simulation always advances one instruction. Similarly to an OS scheduler where several processes share the same CPU time, the OVPsim engine simulates each model instance (i.e., processor, core, peripheral) for a fixed-length block of instructions called Quantum. The quantum size is configurable using a variable, time-slice, representing a time in seconds.3 The quantum size is given by the following equation where by default the time-slice is 0.001 s (1 ms):

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