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Publication . 2018

Powernightmares: The Challenge of Efficiently Using Sleep States on Multi-core Systems

Thomas Ilsche; Marcus Hähnel; Robert Schöne; Mario Bielert; Daniel Hackenberg;
Closed Access
Published: 01 Jan 2018
Publisher: Springer International Publishing
Abstract
Sleep states are an important and well-understood feature of modern server and desktop CPUs that enable significant power savings during idle and partial load scenarios. Making proper decisions about how to use this feature remains a major challenge for operating systems since it requires a trade-off between potential energy-savings and performance penalties for long and short phases of inactivity, respectively. In this paper we analyze the default behavior of the Linux kernel in this regard and identify weaknesses of certain default assumptions. We derive pathological patterns that trigger these weaknesses and lead to ‘Powernightmares’ during which power-saving sleep states are used insufficiently. Our analysis of a workstation and a large supercomputer reveals that these scenarios are relevant on real-life systems in default configuration. We present a methodology to analyze these effects in detail despite their inherent nature of being hardly observable. Finally, we present a concept to mitigate these problems and reclaim lost power saving opportunities.
Subjects by Vocabulary

Microsoft Academic Graph classification: Sleep (system call) Linux kernel Computer science Feature (machine learning) Workstation law.invention law Multi-core processor Idle Efficient energy use Supercomputer Risk analysis (engineering)

Funded by
EC| READEX
Project
READEX
Runtime Exploitation of Application Dynamism for Energy-efficient eXascale computing
  • Funder: European Commission (EC)
  • Project Code: 671657
  • Funding stream: H2020 | RIA
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