FLIN: Enabling fairness and enhancing performance in modern NVMe solid state drives

Arash Tavakkol, Mohammad Sadrosadati, Saugata Ghose, Jeremie S. Kim, Yixin Luo, Yaohua Wang, Nika Mansouri Ghiasi, Lois Orosa, Juan Gómez-Luna, Onur Mutlu

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Modern solid-state drives (SSDs) use new host–interface protocols, such as NVMe, to provide applications with fast access to storage. These new protocols make use of a concept known as the multi-queue SSD (MQ-SSD), where the SSD has direct access to the application-level I/O request queues. This removes most of the OS software stack that was used in older protocols to control how and when the I/O requests were dispatched to storage devices. Unfortunately, while the elimination of the OS software stack leads to a significant performance improvement, we show in this paper that it introduces a new problem: unfairness. This is because the elimination of the OS software stack eliminates the mechanisms that were used to provide fairness among applications in older SSDs. To study application-level unfairness, we perform experiments using four real state-of-the-art MQ-SSDs. We demonstrate that the lack of fair scheduling mechanisms leads to high unfairness among concurrently-executing applications due to the interference among them. For instance, when one of these applications issues many more I/O requests than others, the other applications are slowed down significantly. We perform a comprehensive analysis of interference in real MQ-SSDs, and find four major interference sources: (1) the intensity of requests sent by each application, (2) differences in request access patterns, (3) the ratio of reads to writes, and (4) garbage collection. To alleviate unfairness in MQ-SSDs, we propose the Flash-Level INterference-aware scheduler (FLIN). FLIN is a lightweight I/O request scheduling mechanism that provides fairness among requests from different applications. FLIN uses a three-stage scheduling algorithm that protects against all four major sources of interference, while respecting the application-level priorities assigned by the host. FLIN is implemented fully within the SSD controller firmware, requiring no new hardware, and has negligible (<0.06%) storage cost. Compared to a state-of-the-art I/O scheduler, FLIN improves the fairness and performance of a wide range of enterprise and datacenter storage workloads, with an average improvement of 70% and 47%, respectively.

Original languageEnglish (US)
Title of host publicationProceedings - 2018 ACM/IEEE 45th Annual International Symposium on Computer Architecture, ISCA 2018
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages397-410
Number of pages14
ISBN (Electronic)9781538659847
DOIs
StatePublished - Jul 19 2018
Externally publishedYes
Event45th ACM/IEEE Annual International Symposium on Computer Architecture, ISCA 2018 - Los Angeles, United States
Duration: Jun 2 2018Jun 6 2018

Publication series

NameProceedings - International Symposium on Computer Architecture
ISSN (Print)1063-6897

Other

Other45th ACM/IEEE Annual International Symposium on Computer Architecture, ISCA 2018
Country/TerritoryUnited States
CityLos Angeles
Period6/2/186/6/18

ASJC Scopus subject areas

  • Hardware and Architecture

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