Enlightening the I/O Path: A Holistic Approach for Application Performance


Sangwook Kim, Apposha and Sungkyunkwan University; Hwanju Kim, Sungkyunkwan University and Dell EMC; Joonwon Lee and Jinkyu Jeong, Sungkyunkwan University


In data-intensive applications, such as databases and keyvalue stores, reducing the request handling latency is important for providing better data services. In such applications, I/O-intensive background tasks, such as checkpointing, are the major culprit in worsening the latency due to the contention in shared I/O stack and storage. To minimize the contention, properly prioritizing I/Os is crucial but the effectiveness of existing approaches is limited for two reasons. First, statically deciding the priority of an I/O is insufficient since high-priority tasks can wait for low-priority I/Os due to I/O priority inversion. Second, multiple independent layers in modern storage stacks are not holistically considered by existing approaches which thereby fail to effectively prioritize I/Os throughout the I/O path.

In this paper, we propose a request-centric I/O prioritization that dynamically detects and prioritizes I/Os delaying request handling at all layers in the I/O path. The proposed scheme is implemented on Linux and is evaluated with three applications, PostgreSQL, MongoDB, and Redis. The evaluation results show that our scheme achieves up to 53% better request throughput and 42× better 99th percentile request latency (84 ms vs. 3581 ms), compared to the default configuration in Linux.

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@inproceedings {202259,
author = {Sangwook Kim and Hwanju Kim and Joonwon Lee and Jinkyu Jeong},
title = {Enlightening the I/O Path: A Holistic Approach for Application Performance},
booktitle = {15th {USENIX} Conference on File and Storage Technologies ({FAST} 17)},
year = {2017},
isbn = {978-1-931971-36-2},
address = {Santa Clara, CA},
pages = {345--358},
url = {https://www.usenix.org/conference/fast17/technical-sessions/presentation/kim-sangwook},
publisher = {{USENIX} Association},