A Functionality-Based Runtime Relocation System for Circuits on Heterogeneous FPGAs

Runtime relocation of circuits on field-programmable gate arrays (FPGAs) has been proposed for achieving many desirable features including fault tolerance, defragmentation, and system load balancing. However, the changes in the architectural composition of FPGAs have made relocation more challenging mainly because FPGAs have become more heterogeneous. Previous and state-of-the-art circuit relocation systems on FPGAs have relied only on direct bitstream relocation which requires the source and destination resource layouts to be the same, as well as access to the design bitstream for manipulation. Hence, their efficiency on modern heterogeneous chips greatly reduces, and mostly cannot be applied to encrypted bitstreams of intellectual property blocks. In this brief, we present a circuit relocator which augments direct bitstream relocation with a functionality-based relocation scheme. We demonstrate the feasibility of the proposed technique using a CORDIC application and show that an average of over 2.6-fold increase in the number of relocations can be obtained compared to only direct bitstream relocation at the expense of a small memory overhead and manageable relocation time for this case study

Interconnect architectures for dynamically partially reconfigurable systems

Dynamically partially reconfigurable FPGAs (Field-Programmable Gate Arrays) allow hardware modules to be placed and removed at runtime while other parts of the system keep working. With their potential benefits, they have been the topic of a great deal of research over the last decade. To exploit the partial reconfiguration capability of FPGAs, there is a need for efficient, dynamically adaptive communication infrastructure that automatically adapts as modules are added to and removed from the system. Many bus and network-on-chip (NoC) architectures have been proposed to exploit this capability on FPGA technology. However, few realizations have been reported in the public literature to demonstrate or compare their performance in real world applications. While partial reconfiguration can offer many benefits, it is still rarely exploited in practical applications. Few full realizations of partially reconfigurable systems in current FPGA technologies have been published. More application experiments are required to understand the benefits and limitations of implementing partially reconfigurable systems and to guide their further development. The motivation of this thesis is to fill this research gap by providing empirical evidence of the cost and benefits of different interconnect architectures. The results will provide a baseline for future research and will be directly useful for circuit designers who must make a well-reasoned choice between the alternatives. This thesis contains the results of experiments to compare different NoC and bus interconnect architectures for FPGA-based designs in general and dynamically partially reconfigurable systems. These two interconnect schemes are implemented and evaluated in terms of performance, area and power consumption using FFT (Fast Fourier Transform) andANN(Artificial Neural Network) systems as benchmarks. Conclusions drawn from these results include recommendations concerning the interconnect approach for different kinds of applications. It is found that a NoC provides much better performance than a single channel bus and similar performance to a multi-channel bus in both parallel and parallel-pipelined FFT systems. This suggests that a NoC is a better choice for systems with multiple simultaneous communications like the FFT. Bus-based interconnect achieves better performance and consume less area and power than NoCbased scheme for the fully-connected feed-forward NN system. This suggests buses are a better choice for systems that do not require many simultaneous communications or systems with broadcast communications like a fully-connected feed-forward NN. Results from the experiments with dynamic partial reconfiguration demonstrate that buses have the advantages of better resource utilization and smaller reconfiguration time and memory than NoCs. However, NoCs are more flexible and expansible. They have the advantage of placing almost all of the communication infrastructure in the dynamic reconfiguration region. This means that different applications running on the FPGA can use different interconnection strategies without the overhead of fixed bus resources in the static region. Another objective of the research is to examine the partial reconfiguration process and reconfiguration overhead with current FPGA technologies. Partial reconfiguration allows users to efficiently change the number of running PEs to choose an optimal powerperformance operating point at the minimum cost of reconfiguration. However, this brings drawbacks including resource utilization inefficiency, power consumption overhead and decrease in system operating frequency. The experimental results report a 50% of resource utilization inefficiency with a power consumption overhead of less than 5% and a decrease in frequency of up to 32% compared to a static implementation. The results also show that most of the drawbacks of partial reconfiguration implementation come from the restrictions and limitations of partial reconfiguration design flow. If these limitations can be addressed, partial reconfiguration should still be considered with its potential benefits.Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 201

Design Optimizations for Tiled Partially Reconfigurable Systems

Koester M, Luk W, Hagemeyer J, Porrmann M, Rückert U. Design Optimizations for Tiled Partially Reconfigurable Systems. IEEE Transactions on Very Large Scale Integration (VLSI) Systems. 2010;19(6):1048-1061.In partially reconfigurable architectures, system components can be dynamically loaded and unloaded allowing resources to be shared over time. Dynamic system components are represented by partial reconfiguration (PR) modules. In comparison to a static system, the design of a partially reconfigurable system requires additional design steps, such as partitioning the device resources into static and dynamic regions. We present the concept of tiled PR regions, which enables a flexible online-placement of PR modules. Dynamic reconfiguration requires a suitable communication infrastructure to interconnect the static and dynamic system components. We present an embedded communication macro, a communication infrastructure that interconnects PR modules in a tiled PR region. Efficient online-placement of PR modules depends not only on the placement algorithm, but also on design-time aspects such as the chosen synthesis regions of the PR modules. We propose a design method for selecting suitable synthesis regions for the PR modules aiming to optimize their placement at run-time

Efficient runtime placement management for high performance and reliability in COTS FPGAs

Designing high-performance, fault-tolerant multisensory electronic systems for hostile environments such as nuclear plants and outer space within the constraints of cost, power and flexibility is challenging. Issues such as ionizing radiation, extreme temperature and ageing can lead to faults in the electronics of these systems. In addition, the remote nature of these environments demands a level of flexibility and autonomy in their operations. The standard practice of using specially hardened electronic devices for such systems is not only very expensive but also has limited flexibility. This thesis proposes novel techniques that promote the use of Commercial Off-The- Shelf (COTS) reconfigurable devices to meet the challenges of high-performance systems for hostile environments. Reconfigurable hardware such as Field Programmable Gate Arrays (FPGA) have a unique combination of flexibility and high performance. The flexibility offered through features such as dynamic partial reconfiguration (DPR) can be harnessed not only to achieve cost-effective designs as a smaller area can be used to execute multiple tasks, but also to improve the reliability of a system as a circuit on one portion of the device can be physically relocated to another portion in the case of fault occurrence. However, to harness these potentials for high performance and reliability in a cost-effective manner, novel runtime management tools are required. Most runtime support tools for reconfigurable devices are based on ideal models which do not adequately consider the limitations of realistic FPGAs, in particular modern FPGAs which are increasingly heterogeneous. Specifically, these tools lack efficient mechanisms for ensuring a high utilization of FPGA resources, including the FPGA area and the configuration port and clocking resources, in a reliable manner. To ensure high utilization of reconfigurable device area, placement management is a key aspect of these tools. This thesis presents novel techniques for the management of hardware task placement on COTS reconfigurable devices for high performance and reliability. To this end, it addresses design-time issues that affect efficient hardware task placement, with a focus on reliability. It also presents techniques to maximize the utilization of the FPGA area in runtime, including techniques to minimize fragmentation. Fragmentation leads to the creation of unusable areas due to dynamic placement of tasks and the heterogeneity of the resources on the chip. Moreover, this thesis also presents an efficient task reuse mechanism to improve the availability of the internal configuration infrastructure of the FPGA for critical responsibilities like error mitigation. The task reuse scheme, unlike previous approaches, also improves the utilization of the chip area by offering defragmentation. Task relocation, which involves changing the physical location of circuits is a technique for error mitigation and high performance. Hence, this thesis also provides a functionality-based relocation mechanism for improving the number of locations to which tasks can be relocated on heterogeneous FPGAs. As tasks are relocated, clock networks need to be routed to them. As such, a reliability-aware technique of clock network routing to tasks after placement is also proposed. Finally, this thesis offers a prototype implementation and characterization of a placement management system (PMS) which is an integration of the aforementioned techniques. The performance of most of the proposed techniques are tested using data processing tasks of a NASA JPL spectrometer application. The results show that the proposed techniques have potentials to improve the reliability and performance of applications in hostile environment compared to state-of-the-art techniques. The task optimization technique presented leads to better capacity to circumvent permanent faults on COTS FPGAs compared to state-of-the-art approaches (48.6% more errors were circumvented for the JPL spectrometer application). The proposed task reuse scheme leads to approximately 29% saving in the amount of configuration time. This frees up the internal configuration interface for more error mitigation operations. In addition, the proposed PMS has a worst-case latency of less than 50% of that of state-of- the-art runtime placement systems, while maintaining the same level of placement quality and resource overhead