Data structures for non-volatile memories have to be designed such that they can be atomically modified using transactions. Existing atomicity methods require data to be copied in the critical path which significantly increases the latency of transactions. These overheads are further amplified for transactions on byte-addressable persistent memories where often the byte ranges modified for data structure updates are significantly smaller compared to the granularity at which data can be efficiently copied and logged. We propose Kamino-Tx that provides a new way to perform transactional updates on non-volatile byte-addressable memories (NVM) without requiring any copying of data in the critical path. Kamino-Tx maintains an additional copy of data off the critical path to achieve atomicity. But in doing so Kamino-Tx has to overcome two important challenges of safety and minimizing NVM storage overhead. We propose a more dynamic approach to maintaining the additional copy of data to reduce storage overheads. To further mitigate the storage overhead of using Kamino-Tx in a replicated setting, we develop Kamino-Tx-Chain, a variant of Chain Replication where replicas perform in-place updates and do not maintain data copies locally; replicas in Kamino-Tx-Chain leverage other replicas as copies to roll back or forward for atomicity. Our results show that using Kamino-Tx increases throughput by up to 9.5x for unreplicated systems and up to 2.2x for replicated settings.

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Applications can map data on SSDs into virtual memory to transparently scale beyond DRAM capacity, permitting them to leverage high SSD capacities with few code changes. Obtaining good performance for memory-mapped SSD content, however, is hard because the virtual memory layer, the file system and the flash translation layer (FTL) perform address translations, sanity and permission checks independently from each other. We introduce FlashMap, an SSD interface that is optimized for memory-mapped SSD-files. FlashMap combines all the address translations into page tables that are used to index files and also to store the FTL-level mappings without altering the guarantees of the file system or the FTL. It uses the state in the OS memory manager and the page tables to perform sanity and permission checks respectively. By combining these layers, FlashMap reduces critical-path latency and improves DRAM caching efficiency. We find that this increases performance for applications by up to 3.32x compared to state-of-the-art SSD file-mapping mechanisms. Additionally, latency of SSD accesses reduces by up to 53.2%.

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Today's cloud storage stack is extremely resource hungry, burning 10-20% of datacenter x86 cores, a major "storage tax" that cloud providers must pay. Yet, the complex cloud storage stack is not completely offload-ready to today's IO accelerators. We present LeapIO, a new cloud storage stack that leverages ARM-based co-processors to offload complex storage services. LeapIO addresses many deployment challenges, such as hardware fungibility, software portability, virtualizability, composability, and efficiency. It uses a set of OS/software techniques and new hardware properties that provide a uniform address space across the x86 and ARM cores and expose virtual NVMe storage to unmodified guest VMs, at a performance that is competitive with bare-metal servers. CCS Concepts. • Computer systems organization → Cloud computing; Client-server architectures; System on a chip; Real-time system architecture.

Applications can map data on SSDs into virtual memory to transparently scale beyond DRAM capacity, permitting them to leverage high SSD capacities with few code changes. Obtaining good performance for memory-mapped SSD content, however, is hard because the virtual memory layer, the file system and the flash translation layer (FTL) perform address translations, sanity and permission checks independently from each other. We introduce FlashMap, an SSD interface that is optimized for memory-mapped SSD-files. FlashMap combines all the address translations into page tables that are used to index files and also to store the FTL-level mappings without altering the guarantees of the file system or the FTL. It uses the state in the OS memory manager and the page tables to perform sanity and permission checks respectively. By combining these layers, FlashMap reduces critical-path latency and improves DRAM caching efficiency. We find that this increases performance for applications by up to 3.32x compared to state-of-the-art SSD file-mapping mechanisms. Additionally, latency of SSD accesses reduces by up to 53.2%.

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