An Analysis of User-space Idle State Instructions on x86 Processors

Research output: Contribution to book/Conference proceedings/Anthology/ReportConference contributionContributedpeer-review

Contributors

Abstract

Power consumption has become a limiting factor in all areas of computing. Hence, making the most of the available power budget is paramount. To use the available budget most efficiently, techniques like dynamic voltage and frequency scaling and idle states can be used. This work analyzes the instructions UMWAIT, TPAUSE, and MWAITX on three different systems. We analyze their instruction latencies, power consumptions, and dependencies on core frequencies. To do so, we introduce benchmarks to gather performance and power parameters, which can be used for future software optimizations. Key findings include: The expected sleep duration passed to UMWAIT and TPAUSE can influence the depth of the user idle state. The actual sleep duration of TPAUSE increases stepwise with an increasing expected sleep duration. Requesting a deeper idle state leads to an additional sleep duration, which increases with a lower core frequency. The core frequency influences the instruction latency of TPAUSE, where a low frequency can lead to an irregular performance pattern. The latency of TPAUSE, UMWAIT, and MWAITX is most often higher than requested on the evaluated systems. Core power consumption can be reduced by ∼20% ∼70% compared to the usage of PAUSE. The latency for waking a core in user idle reflects the underlying hardware architecture with tens (desktop architecture with shallow idle states) to hundreds (server architecture with deep idle states) of nanoseconds at nominal frequencies.

Details

Original languageEnglish
Title of host publicationICPE 2025 - Proceedings of the 16th ACM/SPEC International Conference on Performance
PublisherAssociation for Computing Machinery, Inc
Pages232-239
Number of pages8
ISBN (electronic)9798400710735
Publication statusPublished - 5 May 2025
Peer-reviewedYes

Publication series

SeriesICPE: ACM/SPEC International Conference on Performance Engineering

Conference

Title16th ACM/SPEC International Conference on Performance
Abbreviated titleICPE 2025
Conference number16
Duration5 - 9 May 2025
Website
LocationYork University
CityToronto
CountryCanada

External IDs

ORCID /0000-0001-9601-8683/work/186621393

Keywords

Sustainable Development Goals

Keywords

  • energy efficiency, mwaitx, tpause, umwait, user-space idle states