Exploiting intra-request slack to improve SSD performance

Nima Elyasi, Mohammad Arjomand, Anand Sivasubramaniam, Mahmut T. Kandemir, Chita R. Das, Myoungsoo Jung

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

With Solid State Disks (SSDs) offering high degrees of parallelism, SSD controllers place data and direct requests to exploit the maximum offered hardware parallelism. In the quest to maximize parallelism and utilization, sub-requests of a request that are directed to different flash chips by the scheduler can experience differential wait times since their individual queues are not coordinated and load balanced at all times. Since the macro request is considered complete only when its last sub-request completes, some of its sub-requests that complete earlier have to necessarily wait for this last sub-request. This paper opens the door to a new class of schedulers to leverage such slack between sub-requests in order to improve response times. Specifically, the paper presents the design and implementation of a slack-enabled re-ordering scheduler, called Slacker, for sub-requests issued to each flash chip. Layered under a modern SSD request scheduler, Slacker estimates the slack of each incoming sub-request to a flash chip and allows them to jump ahead of existing sub-requests with sufficient slack so as to not detrimentally impact their response times. Slacker is simple to implement and imposes only marginal additions to the hardware. Using a spectrum of 21 workloads with diverse read-write characteristics, we show that Slacker provides as much as 19.5%, 13% and 14.5% improvement in response times, with average improvements of 12%, 6.5% and 8.5%, for write-intensive, read-intensive and read-write balanced workloads, respectively.

Original languageEnglish
Pages (from-to)375-388
Number of pages14
JournalACM SIGPLAN Notices
Volume52
Issue number4
DOIs
Publication statusPublished - 2017 Apr 4

All Science Journal Classification (ASJC) codes

  • Computer Science(all)

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  • Cite this

    Elyasi, N., Arjomand, M., Sivasubramaniam, A., Kandemir, M. T., Das, C. R., & Jung, M. (2017). Exploiting intra-request slack to improve SSD performance. ACM SIGPLAN Notices, 52(4), 375-388. https://doi.org/10.1145/3037697.3037728