Vigil-KV: Hardware-Software Co-Design to Integrate Strong Latency Determinism into Log-Structured Merge Key-Value Stores


Miryeong Kwon, Seungjun Lee, and Hyunkyu Choi, KAIST; Jooyoung Hwang, Samsung Electronics Co., Ltd.; Myoungsoo Jung, KAIST


We propose \emph{Vigil-KV}, a hardware and software co-designed framework that eliminates long-tail latency almost perfectly by introducing strong latency determinism. To make Get latency deterministic, Vigil-KV first enables a predictable latency mode (PLM) interface on a real datacenter-scale NVMe SSD, having knowledge about the nature of the underlying flash technologies. Vigil-KV at the system-level then hides the non-deterministic time window (associated with SSD's internal tasks and/or write services) by internally scheduling the different device states of PLM across multiple physical functions. Vigil-KV further schedules compaction/flush operations and client requests being aware of PLM's restrictions thereby integrating strong latency determinism into LSM KVs. We implement Vigil-KV upon a 1.92TB NVMe SSD prototype and Linux 4.19.91, but other LSM KVs can adopt its concept. We evaluate diverse Facebook and Yahoo scenarios with Vigil-KV, and the results show that Vigil-KV can reduce the tail latency of a baseline KV system by 3.19 times while reducing the average latency by 34%, on average.

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@inproceedings {280804,
author = {Miryeong Kwon and Seungjun Lee and Hyunkyu Choi and Jooyoung Hwang and Myoungsoo Jung},
title = {{Vigil-KV}: {Hardware-Software} {Co-Design} to Integrate Strong Latency Determinism into {Log-Structured} Merge {Key-Value} Stores},
booktitle = {2022 USENIX Annual Technical Conference (USENIX ATC 22)},
year = {2022},
isbn = {978-1-939133-29-71},
address = {Carlsbad, CA},
pages = {755--772},
url = {},
publisher = {USENIX Association},
month = jul

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