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White paperCitation2021

WP#84 - Trade-offs of Processor Power Management Functions of Servers

The Green Grid

The Green Grid paper quantifying the gains and costs of CPU P-state and C-state power management.

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Overview

This document is The Green Grid (TGG) white paper number 84, dated 28 April 2021. It quantifies the trade-offs of CPU P-state and C-state power management. According to the paper, with full P-state and C-state implementation power demand can fall by up to 50% at low utilisation, and SERT overall efficiency scores can improve by up to 30%.

Access requires registration; only the information on the description page was used here. The gain comes at the cost of reduced performance and increased exit latency. At 100% utilisation with power management on, performance fell 5.6% on EPYC and 14.3% on Power9. The savings therefore depend on the load profile: they are marked at low utilisation, while at full load there is a performance cost.

The paper also notes that some workloads may need power management turned off, among them high-frequency trading (HFT), network and high-performance computing (HPC) workloads. Its limit is that the figures rest on two processor families, so the results should not be generalised directly to other hardware and must be verified on the target platform.

Key points

  1. Dated 28 April 2021.
  2. Full P-state and C-state implementation can cut power demand by up to 50%.
  3. SERT overall efficiency scores improve by up to 30%.
  4. At 100% utilisation, performance fell 5.6% (EPYC) and 14.3% (Power9) with power management on.
  5. Savings come at the cost of reduced performance and increased exit latency.
  6. HFT, network and HPC workloads may need power management turned off.
  7. Registration required.

Using it in design

  • In the IT load profile, provide an idle/low-utilisation power factor that depends on whether CPU power management is enabled.
  • Do not assume savings for HPC and AI archetypes.
  • Report power-management savings together with the usage scenario.

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Who should read it

Designers who build IT load profiles and size cooling and power, and server efficiency teams.

Publication details

Authors
The Green Grid
Publisher
The Green Grid
Year
2021
Document number
WP 84
Document language
English
Source type
Industry body
Access
Citation only
Licence
Copyright retained; citation only — the publisher’s terms apply to the original document
Original licence note

Download requires a free TGG account sign-in and is governed by The Green Grid Terms of Use; summary and facts from the public library landing page; full text not redistributed.

Citation

The Green Grid (2021). WP#84 - Trade-offs of Processor Power Management Functions of Servers. The Green Grid. WP 84. https://www.thegreengrid.org/en/resources/library-and-tools/521-WP%2384---TRADE-OFFS-OF-PROCESSOR-POWER-MANAGEMENT-FUNCTIONS-OF-SERVERS

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