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Traditional Linux prefetching algorithms were based on spatial locality of I/O workloads and performance model of hard disk drives. From the applicative point of view, current data-intensive applications I/O workloads are turning towards more random patterns while from the storage device perspective, flash based storage devices present a different performance model than HDDs. In this work, we present...
Mobile devices are playing important roles in people's daily life. For mobile devices, system responsiveness is of great importance to keep an impressive user experience. Although new technologies have been developed to improve system responsiveness, mobile devices still suffer from various unpredictable delay. Recently, our evaluation reveals that improper merging operations happen in I/O scheduler...
Persistent memory (PM) is rapidly emerging as a promising technology with its useful properties such as durability, DRAM-like performance, and byte addressability. However, programming PM is challenging because programmers need to manually orchestrate all the persists with the cache flush operations and persist barriers to ensure the correct execution of their code. To improve the programmability...
Modern microprocessors have increased the word width to 64-bits to support larger main memory sizes. It has been observed that data can often be represented by relatively few bits, so-called narrow-width values. To leverage narrow-width data, we propose a hybrid cache architecture composed of magnetic RAM (MRAM) and SRAM to save the upper and lower 32-bits of each word in MRAM and SRAM respectively...
Phase-change memory (PCM) is a potential candidate to replace flash memory in the storage design of mobile computing systems, but its energy consumption becomes a challenging issue when the multi-level cell (MLC) technology is adopted to reduce its unit cost. In contrast to the existing works that focus on reducing energy consumption at the hardware/device level, we propose an energy-aware memory...
An object-based NAND flash storage system (ONFS) is proposed to overcome the architectural limitation of the existing block-based storage system. The ONFS can improve system performance by removing redundant software layers and reducing garbage collection overhead. However, the research progress of ONFS is significantly hindered due to lack of appropriate simulation tools. In this work, we present...
For SSD-based RAID systems, the Diff-RAID technique has been proposed to reduce the probability of correlated multiple failures among SSDs by differentiating the amount of written data to each SSD. Although Diff-RAID works well for workloads with many small random writes (which require frequent parity updates), it does not perform well with recent data center workloads (e.g., key-value stores) which...
Atomic and durable transactions are widely used to ensure the crash consistency in persistent memory (PM). However, whether to use redo or undo logging is still a hotly debated topic in persistent memory systems. In this paper, we empirically study the performance of both redo and undo logging using NVML, a persistent memory transactional object store framework. Our results on an NVDIMM server show...
Non-Volatile Memory Express (NVMe) is designed with the goal of unlocking the potential of low-latency, randomaccess, memory-based storage devices. Specifically, NVMe employs various rich communication and queuing mechanism that can ideally schedule four billion I/O instructions for a single storage device. To explore NVMe with assorted user scenarios, we model diverse interface-level design parameters...
Non-volatile memory (NVM) enables intermittent systems without batteries because of the persistence of NVM. However, the persistence presents a new challenge to memory consistency threatening to corrupt application data across a power failure. Prior work proposes various software-based techniques built upon compiler instrumentation to achieve memory consistency. However, those techniques are not only...
The number of Internet of Things (IoT) devices is exhibiting explosive growth. These devices are often closely coupled to the physical world, and may harvest energy as a power source, which imposes particularly stringent operating constraints. Like any programmable system, IoT devices may need software updates to fix bugs, add functionality, or improve computational capability. This paper proposes...
Appealed by the market, flash memory density is being increasingly improved, and the technology scale is being reduced. Currently, scaled multi-level-cell (MLC) flash memory has been the dominant in the global flash memory markets. However, the reliability of MLC flash memory becomes the urgent challenge, where cell-to-cell interference has been well recognized as the major error source. In this work,...
The file accesses of existing in-memory file systems have additional costs for traversing the software stacks of the kernel, such as VFS. To avoid such costs, the existing file systems generally enable user-space file accesses using the memorymapped file (mmap) techniques. The mmap approaches, however, are add-ons of the file systems in the kernel level that have large overhead for mapping the files...
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