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Sound source localization (SSL) has been widely applied in industrial and civil fields. And with the development of wearable devices and the Internet of Things (IoT), it is attractive to deploy the SSL system onto embedded and portable devices. However, the software-based SSL system causes excessive response delay and is often affected by environmental noise. To overcome this obstacle, we propose the fast and precise localization (FPL) algorithm for distributed SSL systems. It combines the benefits of both time difference of arrival (TDOA) and steered response power (SRP) methods, and thus it is able to localize sound sources fast and precisely. To further improve the localization speed, we propose the fast and reconfigurable localization (FRL) accelerator, which is an algorithm-hardware co-designed SSL accelerator. It adopts multiple distributed localization nodes for higher localization precision and higher robustness to environmental interference, and it can be configured into either the fast or precise mode to adapt to various environments. Experimental evaluations show that our proposed FPL algorithm can achieve high localization speed and precision, and the field-programmable gate array (FPGA)-based FRL accelerator outperforms the software implementation by $48.6\times $ and outperforms the prior FPGA-based SSL accelerators by $20\times \sim 838.2\times $. [ABSTRACT FROM AUTHOR]

Emerging autonomous vehicles equip multiple high-throughput sensors to enable automatic driving, such as multiline lidars and high-definition cameras. Existing automotive embedded systems usually employ software stacks to receive and preprocess high-throughput sensor data, which brings high latency and CPU consumption. Most research is devoted to accelerators for data processing but ignores the latency overhead caused by sensor data access. Therefore, this article proposes SENTunnel to build fast path from sensors to the corresponding processing units by offloading redundant software stacks into hardware. Specifically, SENTunnel builds fast path for sensor data access to processors/accelerators through two hardware modules. First, the unified access module is used to receive, parse, and transmit raw sensor data. Second, SENTunnel performs necessary preprocessing of different sensor data with the preprocessors module. Based on the design of SENTunnel, we implement a prototype for accessing the data of multiline lidars to the processor and a dedicated accelerator on FPGA. Experimental results indicate that SENTunnel reduces the latency by 55.5% for the data path to processors and reduces the CPU usage caused by the preprocessing driver by 45.9% on average. Compared to the original and partially offloaded data path to accelerators, SENTunnel reduces the latency by 93.8% and 93%, respectively, and eliminates the CPU costs. [ABSTRACT FROM AUTHOR]

Emerging embedded systems, such as autonomous vehicles, demand highly efficient remote data transfer, whereas existing networking hardware and protocols cause high communication latency and CPU consumption. In this article, we propose embedded RDAC (eRDAC), an efficient and reliable remote direct access and control solution for embedded systems. The proposed remote access controller in eRDAC has a two-layer protocol offload engine that employs the command/response protocol on UDP to ensure the data reliability and security, and a multichannel DMA controller with configurable priority to improve the efficiency. Besides, a reusable hardware Ethernet MAC is implemented to support not only remote access commands but also standard Ethernet communication. We implement eRDAC on FPGA and the corresponding software in the Linux system. Experimental results show that eRDAC can reduce the latency of remote I/O reading/writing by 74.3%/74.9% ($3.76\times /3.98\times $ performance improvement) and reduce the latency of remote memory reading and writing with 1024B by 54.2% compared to the socket-based communication. Meanwhile, eRDAC can cut off the consumption of the remote processor and achieve 0.250mJ/Mb energy consumption with only 25-mW power. [ABSTRACT FROM AUTHOR]

Near-data processing (NDP) architecture is promised to break the bottleneck of data movement in many scenarios (e.g., databases and recommendation systems), which limits the efficiency of data processing. Different from traditional SSD, NDP-based SSD not only needs to handle normal I/Os (e.g., read and write), but also needs to handle NDP requests that contain data processing operations. NDP and normal I/O requests share some function units of NDP-based SSD, such as flash chips and embedded processors. However, existing works ignore the resource competition between normal I/Os and NDP requests, which drastically degrades the performance. In this article, we propose a novel scheduling technique called Horae, which can efficiently schedule hybrid NDP-normal I/O requests in NDP-based SSD to improve performance. Horae exploits the critical paths on critical resources to maximize the parallelism of multiple stages of requests. The experimental results on typical workloads show that Horae can significantly improve the performance of hybrid NDP-normal I/O requests over the state-of-the-art scheduling algorithms of NDP-based SSDs. [ABSTRACT FROM AUTHOR]

Federated Learning (FL) enables the multiple participating devices to collaboratively contribute to a global neural network model while keeping the training data locally. Unlike the centralized training setting, the non-IID, imbalanced (statistical heterogeneity) and distribution shifted training data of FL is distributed in the federated network, which will increase the divergences between the local models and the global model, further degrading performance. In this paper, we propose a flexible clustered federated learning (CFL) framework named FlexCFL, in which we 1) group the training of clients based on the similarities between the clients’ optimization directions for lower training divergence; 2) implement an efficient newcomer device cold start mechanism for framework scalability and practicality; 3) flexibly migrate clients to meet the challenge of client-level data distribution shift. FlexCFL can achieve improvements by dividing joint optimization into groups of sub-optimization and can strike a balance between accuracy and communication efficiency in the distribution shift environment. The convergence and complexity are analyzed to demonstrate the efficiency of FlexCFL. We also evaluate FlexCFL on several open datasets and made comparisons with related CFL frameworks. The results show that FlexCFL can significantly improve absolute test accuracy by $+10.6\%$ + 10. 6 % on FEMNIST compared with FedAvg, $+3.5\%$ + 3. 5 % on FashionMNIST compared with FedProx, $+8.4\%$ + 8. 4 % on MNIST compared with FeSEM, $+4.7\%$ + 4. 7 % on Sentiment140 compare with IFCA. The experiment results show that FlexCFL is also communication efficient in the distribution shift environment. [ABSTRACT FROM AUTHOR]

Emerging applications like machine learning in embedded devices (e.g., satellites and vehicles) require huge storage space, which recently stimulates the widespread deployment of large-scale flash memory in IoT devices. However, existing embedded file systems fall short in managing large-capacity storage efficiently for two reasons. First, prior arts store data structures of file systems either in flash or in main memory, which severely magnifies the scarcity of computing and memory resources. Moreover, the fine-grained metadata management in the existing embedded file systems induces significant energy consumption for large-capacity storage. In this paper, we propose a novel embedded file system, ELOFS, to tackle the above issues and manage large-capacity NAND flash on resource-scarce devices. ELOFS is made efficient through three novel techniques. First, we redefine the space management granularity and streamline the metadata to speed up the mounting performance. In addition, we design hybrid file structures to adapt dissimilar access patterns of embedded devices. Furthermore, ELOFS provides opportunities for in-depth cooperation with application-specific systems. We implement ELOFS with Memory Technology Device (MTD) interfaces, and the experimental results show that ELOFS outperforms YAFFS and UBIFS in terms of write, read, and deletions with orders of magnitude reductions on memory footprint and mounting time. [ABSTRACT FROM AUTHOR]

Solid-state drives (SSDs) have been widely deployed in high-performance data center environments, where multiple tenants usually share the same hardware. However, traditional SSDs distribute the users’ incoming data uniformly across all SSD channels, which leads to numerous access conflicts. Meanwhile, SSDs that blindly allocate one or several channels to one tenant sacrifice device parallelism and capacity. When SSDs are shared by tenants with different access patterns, inappropriate channel allocation results in SSD performance degradation. In this article, we propose a self-adapting channel allocation mechanism, named SSDKeeper, for multiple tenants that share one SSD. SSDKeeper employs a machine learning-assisted algorithm to take full advantage of SSD parallelism while providing performance isolation. By collecting multitenant access patterns, SSDKeeper predicts an optimal channel allocation strategy for multiple tenants using the well-trained model. To further consume the blocks in different channels evenly, SSDKeeper equips with a novel channel swap scheme to prolong the SSD lifespan. Comparing with traditional SSDs, SSDKeeper reduces the overall latency of read and write by 12.6% and the lifespan is prolonged up to $3.7\times $. [ABSTRACT FROM AUTHOR]

Translation lookaside buffer (TLB) is critical to modern multi-level memory systems' performance. However, due to the limited size of the TLB itself, its address coverage is limited. Adopting a two-level exclusive TLB hierarchy can increase the coverage [M. Swanson, L. Stoller and J. Carter, Increasing TLB reach using superpages backed by shadow memory, 25th Annual Int. Symp. Computer Architecture (1998); H.P. Chang, T. Heo, J. Jeong and J. Huh Hybrid TLB coalescing: Improving TLB translation coverage under diverse fragmented memory allocations, ACM SIGARCH Comput. Arch. News45 (2017) 444–456] to improve memory performance. However, after analyzing the existing two-level exclusive TLBs, we find that a large number of "dead" entries (they will have no further use) exist in the last-level TLB (LLT) for a long time, which occupy much cache space and result in low TLB hit-rate. Based on this observation, we first propose exploiting temporal and spatial locality to predict and identify dead entries in the exclusive LLT and remove them as soon as possible to leave room for more valid data to increase the TLB hit rates. Extensive experiments show that our method increases the average hit rate by 8.67%, to a maximum of 19.95%, and reduces total latency by an average of 9.82%, up to 24.41%. [ABSTRACT FROM AUTHOR]

The mismatch between logical and physical I/O granularity inhibits the deployment of embedded file systems. Most existing embedded file systems manage logical space with a small unit, which is no longer the case of the flash operation granularity. Manually enlarging the logical I/O granularity of file systems requires enormous transplanting efforts. Moreover, large logical pages signify the write amplification problem, which turns to severe space consumption and performance collapse. This article designs a novel storage middleware, NV-middle, for legacy-embedded file systems with large-capacity flash memories. Legacy-embedded storage schemes can be smoothly transplanted into new platforms with different hardware read/write granularity. Moreover, the legacy optimization schemes can be maximally reserved, without inducing write amplification problems. We implement NV-middle with the state-of-the-art embedded file system, YAFFS2. Comprehensive evaluations show that NV-middle can achieve times of performance improvement over manually transplanted YAFFS2 with various workloads. [ABSTRACT FROM AUTHOR]

Frequent-pattern mining is a common means to reveal the hidden trends behind data. However, most frequent-pattern mining algorithms are designed for dynamic random-access memory (DRAM), instead of nonvolatile memories (NVMs) which are preferred by energy-limited systems. Due to the huge differences between the characteristics of NVMs and those of DRAM, existing frequent-pattern mining algorithms encounter the issues of write amplification and energy waste when they are run on NVMs. Moreover, the design complexity is exaggerated when parallel computing architecture is introduced to speedup the mining process. A scalable, time-efficient, and energy-economic solution to the frequent-pattern mining problem is thus urgently needed. Based on the well-known frequent-pattern tree (FP-tree) approach to frequent-pattern mining, this article proposes parallel EvFP-tree (PevFP-tree), a parallel frequent-pattern mining solution for NVMs. By considering the NVM characteristics, PevFP-tree accelerates the mining process and enhances the energy efficiency, as compared to a straightforward design of FP-trees on the parallel architecture. Moreover, PevFP-tree offers superior scalability in terms of the degrees of parallelism of the mining algorithm and the branching factor of its tree structure. Observing that keys are often sparsely distributed in FP-trees, we also propose a compression technique to PevFP-tree, namely, compressed PevFP-tree (CpevFP-tree), which further enhances the time and energy efficiencies of PevFP-tree. The proposed PevFP-tree and CpevFP-tree are evaluated by a series of experiments based on realistic datasets from diversified application scenarios, where CpevFP-tree achieves 88.73% of performance improvements over a straightforward design of FP-trees in the parallel architecture, and 79.47% of performance improvements over PevFP-tree, on average. [ABSTRACT FROM AUTHOR]

As one of the workload characteristics, the anomaly behaviors in real workload have been recognized as a critical requirement for file system design. In this paper, a set of traces collected from typically realistic file system have been analyzed. The correlation study of I/O request inter-arrival times shows that it is necessary to examine the self-similarity in file system workload. Then the phenomenon of self-similarity which had been initially observed in network and disk I/O workload has also been visually and statistically observed in file system workload. In addition, we implement an I/O series generator in which the inputs are the measured properties of the available trace data. Experimental results show that this model can accurately emulate the complex access arrival behaviors of real file systems, particularly the heavy-tail characteristics. [ABSTRACT FROM AUTHOR]

We have witnessed the tremendous success of deep neural networks. However, this success comes with the considerable memory and computational costs which make it difficult to deploy these networks directly on resource-constrained embedded systems. To address this problem, we propose TaijiNet, a separable binary network, to reduce the storage and computational overhead while maintaining a comparable accuracy. Furthermore, we also introduce a strategy called partial binarized convolution which binarizes only unimportant kernels to efficiently balance network performance and accuracy. Our approach is evaluated on the CIFAR-10 and ImageNet datasets. The experimental results show that with the proposed TaijiNet, the separable binary versions of AlexNet and ResNet-18 can achieve 26× and 6.4× compression rates with comparable accuracy when comparing with the full-precision versions respectively. In addition, by adjusting the PCA threshold, the xnor version of Taiji-AlexNet improves accuracy by 4-8 percent comparing with other state-of-the-art methods. [ABSTRACT FROM AUTHOR]

In deduplication-based backup systems, the removal of redundant data transforms the otherwise logically adjacent data chunks into physically scattered chunks on the disks. This, in effect, changes the retrieval operations from sequential to random and significantly degrades the performance of restoring data. These scattered chunks are called fragmented data and many techniques have been proposed to identify and sequentially rewrite such fragmented data to new address areas, trading off the increased storage space for reduced number of random reads (disk seeks) to improve the restore performance. However, existing solutions for backup workloads share a common assumption that every read operation involves a large fixed-size window of contiguous chunks, which restricts the fragment identification to a fixed-size read window. This can lead to inaccurate identifications due to false positives since the data fragments can vary in size and appear in any different and unpredictable address locations. Based on these observations, we propose FGdefrag, a Fine-Grained defragmentation approach that uses variable-sized and adaptively located data groups, instead of using fixed-size read windows, to accurately identify and effectively remove fragmented data. When we compare its performance to those of existing solutions, FGdefrag not only reduces the amount of rewritten data but also significantly improves the restore performance. Our experimental results show that FGdefrag can improve the restore performance by 14 to 329 percent, while simultaneously reducing the rewritten data by 25 to 87 percent. [ABSTRACT FROM AUTHOR]