Two-Phase Low-Energy N-Modular Redundancy for Hard Real-Time Multi-Core Systems

Abstract

Abstract-This paper proposes an N-modular redundancy (NMR) technique with low energy-overhead for hard real-time multicore systems. NMR is well-suited for multi-core platforms as they provide multiple processing units and low-overhead communication for voting. However, it can impose considerable energy overhead and hence its energy overhead must be controlled, which is the primary consideration of this paper. For this purpose the system operation can be divided into two phases: indispensable phase and on-demand phase. In the indispensable phase only half-plus-one copies for each task are executed. When no fault occurs during this phase, the results must be identical and hence the remaining copies are not required. Otherwise, the remaining copies must be executed in the on-demand phase to perform a complete majority voting. In this paper, for such a two-phase NMR, an energy-management technique is developed where two new concepts have been considered: i) Block-partitioned scheduling that enables parallel task execution during on-demand phase, thereby leaving more slack for energy saving, ii) Pseudo-dynamic slack, that results when a task has no faulty execution during the indispensable phase and hence the time which is reserved for its copies in the on-demand phase is reclaimed for energy saving. The energymanagement technique has an off-line part that manages static and pseudo-dynamic slacks at design time and an online part that mainly manages dynamic slacks at run-time. Experimental results show that the proposed NMR technique provides up to 29% energy saving and is 6 orders of magnitude higher reliable as compared to a recent previous work.

Peak-Power-Aware Primary-Backup Technique for Efficient Fault-Tolerance in Multicore Embedded Systems

“…3) Tasks Execution (Run time): Figure 4b shows the maximum power consumed by the system in the worstcase fault scenario where all the original and redundant tasks are executed completely. However, at run time, when during the execution of a task no fault occurs, i.e., the predominant execution scenario [50], the execution of the second copy of the task will be cancelled. Figure 4c shows the case where no fault occurs during the execution of the tasks.…”

“…To realize a wide range of competing real-world application scenarios, we selected several benchmark applications from different program groups of MiBench [49] including automotive, consumer, network, office, security and telecommunication. The MiBench Benchmark suite has been widely used in previous related works [1] [18] [50].…”

“…The workload values determine the cores' utilization in the experiment (e.g., for the workload L=0.6 the utilization of each core is considered to be 0.6). For each workload value, we generated 100 task sets from the tasks in Figure 6 and the average results were reported, similar to [50]. We also considered different chips with m=4, 8 and 16 cores and with different TDP values.…”

Multi-objective redundancy hardening with optimal task mapping for independent tasks on multi-cores

“…To achieve reliability against transient faults, three types of redundancies have conventionally been applied, i.e., time redundancy, space redundancy, and hybrid redundancy. Time redundancy (i.e., re-execution) is based on checkpointing and to execute the task again in case of a fault (Kandasamy et al 2003;Nikolov and Larsson 2016;Salehi et al 2016a); it is applicable only after a fault can be detected. The overhead of local fault detection is not free since it is hard to achieve perfect transient fault detection.…”

Fault-Tolerant Task Scheduling for Mixed-Criticality Real-Time Systems

“…10 In particular, fault-tolerance is imperative in the design of such systems to¯ght against potential failures for achieving high safety and reliability. There are many fault-tolerant techniques such as dual/triple modular redundancy, 11,12 re-execution, 13,14 and checkpointing with rollback 15,16 widely used in handling the occurrence of faults. Dual/triple modular redundancy is usually considered to achieve reliability against transient faults in multicore platforms, where multiple processing units execute identical copies for each task and their results are voted on to produce a single output.…”