Writes Hurt: Lessons in Cache Design for Optane NVRAM Article Swipe

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Alexandra Fedorova , Keith Smith , Keith Bostic , Alexander Gorrod , Sue LoVerso , Michael J. Cahill · YOU? · · 2022 · Open Access · · DOI: https://doi.org/10.48550/arxiv.2205.14122

Intel OptaneTM DC Persistent Memory resides on the memory bus and approaches DRAM in access latency. One avenue for its adoption is to employ it in place of persistent storage; another is to use it as a cheaper and denser extension of DRAM. In pursuit of the latter goal, we present the design of a volatile Optane NVRAM cache as a component in a storage engine underlying MongoDB. The primary innovation in our design is a new cache admission policy. We discover that on Optane NVRAM, known for its limited write throughput, the presence of writes disproportionately affects the throughput of reads, much more so than on DRAM. Therefore, an admission policy that indiscriminately admits new data (and thus generates writes), severely limits the rate of data retrieval and results in exceedingly poor performance for the cache overall. We design an admission policy that balances the rate of admission with the rate of lookups using dynamically observed characteristics of the workload. Our implementation outperforms OpenCAS (an off-the-shelf Optane-based block cache) in all cases, and Intel Memory Mode in cases where the database size exceeds the available NVRAM. Our cache is decoupled from the rest of the storage engine and uses generic metrics to guide its admission policy; therefore our design can be easily adopted in other systems.

Type

preprint

Language

en

Landing Page

http://arxiv.org/abs/2205.14122

PDF

https://arxiv.org/pdf/2205.14122

OA Status

green

Cited By

2

Related Works

10

OpenAlex ID

https://openalex.org/W4320458597

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OpenAlex ID

https://openalex.org/W4320458597

Canonical identifier for this work in OpenAlex

DOI

https://doi.org/10.48550/arxiv.2205.14122

Digital Object Identifier

Title

Writes Hurt: Lessons in Cache Design for Optane NVRAM

Work title

Type

preprint

OpenAlex work type

Language

en

Primary language

Publication year

2022

Year of publication

Publication date

2022-05-24

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Authors

Alexandra Fedorova, Keith Smith, Keith Bostic, Alexander Gorrod, Sue LoVerso, Michael J. Cahill

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Landing page

https://arxiv.org/abs/2205.14122

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PDF URL

https://arxiv.org/pdf/2205.14122

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Open access

Yes

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OA status

green

Open access status per OpenAlex

OA URL

https://arxiv.org/pdf/2205.14122

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Concepts

Computer science, Cache, Cache pollution, Page cache, Operating system, Non-volatile random-access memory, Dram, Workload, CPU cache, Cache algorithms, Parallel computing, Embedded system, Semiconductor memory, Computer hardware, Computer memory, Memory refresh

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Cited by

2

Total citation count in OpenAlex

Citations by year (recent)

2023: 2

Per-year citation counts (last 5 years)

Related works (count)

10

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