Volume 58, Issue 6 - Invasive Computing / Guest Editor: Jürgen Teich

Multi-Processor Systems-on-a-Chip (MPSoCs) provide sufficient computing power for many applications in scientific as well as embedded applications. Unfortunately, when real-time requirements need to be guaranteed, applications suffer from the interference with other applications, uncertainty of dynamic workload and state of the hardware. Composable application/architecture design and timing analysis is therefore a must for guaranteeing real-time applications to satisfy their timing requirements independent from dynamic workload. Here, Invasive Computing is used as the key enabler for compositional timing analysis on MPSoCs, as it provides the required isolation of resources allocated to each application. On the basis of this paradigm, this work proposes a hybrid application mapping methodology that combines design-time analysis of application mappings with run-time management. Design space exploration delivers several resource reservation configurations with verified real-time guarantees for individual applications. These timing properties can then be guaranteed at run-time, as long as dynamic resource allocations comply with the offline analyzed resource configurations. This article describes our methodology and presents programming, optimization, analysis, and hardware techniques for enforcing timing predictability. A case study illustrates the timing-predictable management of real-time computer vision applications in dynamic robot system scenarios.

The invasive computing paradigm offers applications the possibility to dynamically spread their computation in a multicore/multiprocessor system in a resource-aware way. If applications are assumed to act maliciously, many security problems arise. In this acticle, we discuss different ways to deal with security problems in a resource-aware way. We first formalize the attacker model and the different security requirements that applications may have in multi-core systems. We then survey different hardware and software security mechanisms that can be dynamically configured to guarantee security on demand for invasive applications.

This paper presents an integrated and coordinated cross-layer sensing and optimization flow for distributed dark silicon management for tiled heterogeneous manycores under a critical temperature constraint. We target some of the key challenges in dark silicon for manycores, such as: directly focusing on power density/temperature instead of considering simple per-chip power constraints, considering tiled heterogeneous architectures with different types of cores and accelerators, handling the large volumes of raw sensor information, and maintaining scalability. Our solution is separated into three abstraction layers: a sensing layer (involving hardware monitors and pre-processing), a dark silicon layer (that derives thermally-safe mappings and voltage/frequency settings), and an agent layer (used for selecting the parallelism of applications and thread-to-core mapping based on alternatives/constraints from the dark silicon layer).

As a consequence of technology scaling, today's complex multi-processor systems have become more and more susceptible to errors. In order to satisfy reliability requirements, such systems require methods to detect and tolerate errors. This entails two major challenges: (a) providing a comprehensive approach that ensures fault-tolerant execution of parallel applications across different types of resources, and (b) optimizing resource usage in the face of dynamic fault probabilities or with varying fault tolerance needs of different applications. In this paper, we present a holistic and adaptive approach to provide fault tolerance on Multi-Processor System-on-a-Chip (MPSoC) on demand of an application or environmental needs based on invasive computing. We show how invasive computing may provide adaptive fault tolerance on a heterogeneous MPSoC including hardware accelerators and communication infrastructure such as a Network-on-Chip (NoC). In addition, we present (a) compile-time transformations to automatically adopt well-known redundancy schemes such as Dual Modular Redundancy (DMR) and Triple Modular Redundancy (TMR) for fault-tolerant loop execution on a class of massively parallel arrays of processors called as Tightly Coupled Processor Arrays (). Based on timing characteristics derived from our compilation flow, we further develop (b) a reliability analysis guiding the selection of a suitable degree of fault tolerance. Finally, we present (c) a methodology to detect and adaptively mitigate faults in invasive NoCs.

Advancements in the areas of Cloud Computing, Internet of Things (IoT), and hybrid Human-Computer systems have made feasible the creation of a highly integrated human-machine world. The concept of elasticity plays a crucial role in fulfilling this vision, enabling systems to address various requirements reflecting performance, security, and business concerns. However, elastic systems are still in their inception, and numerous challenges need to be addressed in their development and management. In this article we present an overview of our experience on elastic systems, with a focus on elastic cloud systems. In the quest for designing and managing elastic systems, several challenges need to be addressed, such as: (i) enabling the systems to fulfill different requirements from multiple involved stakeholders, (ii) designing elastic systems considering various degrees of elasticity capabilities provided by different technologies and environments, (iii) understanding behavioral relationships in elastic systems, and their effects on stakeholder requirements, (iv) monitoring costs and analyzing cost efficiency of elastic systems, (v) controlling the elasticity of such systems at runtime in order to fulfill stakeholders' requirements, and (vi) supporting system elasticity through operations management. We present the techniques we have adopted in order to tackle the above challenges. We introduce our solution for creating elastic systems, following their complete lifecycle, from design-time to operations management.