1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

A Proper Solution To The Linux ASPM Problem

Michael Larabel

Published on 11 November 2011
Written by Michael Larabel
Page 2 of 3 - 40 Comments

Below is Matthew Garrett's description about this new patch.

Right now we forcibly clear ASPM state on all devices if the BIOS indicates that the feature is not supported. Based on the Microsoft presentation "PCI Express In Depth for Windows Vista and Beyond", I'm starting to think that this may be an error. The implication is that unless the platform grants full control via _OSC, Windows will not touch any PCIe features - including ASPM. In that case clearing ASPM state would be an error unless the platform has granted us that control.

This patch reworks the ASPM disabling code such that the actual clearing of state is triggered by a successful handoff of PCIe control to the OS. The general ASPM code undergoes some changes in order to ensure that the ability to clear the bits isn't overridden by ASPM having already been disabled. Further, this theoretically now allows for situations where only a subset of PCIe roots hand over control, leaving the others in the BIOS state.

It's difficult to know for sure that this is the right thing to do - there's zero public documentation on the interaction between all of these components. But enough vendors enable ASPM on platforms and then set this bit that it seems likely that they're expecting the OS to leave them alone.

Measured to save around 5W on an idle Thinkpad X220.

This ~60 line kernel patch changes the ASPM behavior and from his testing, plus my initial testing, it seems to be relatively sane. From the various notebooks (a half-dozen so far) I have been trying out, there have not been any problems and ASPM is working without having to manually force it.

On the next page is a test of this patch and the system power consumption from one of the ASPM affected systems under the Linux 2.6.37, 2.6.38, 3.2, and 3.2 patched kernels.

Latest Linux Hardware Reviews
  1. Even With Re-Clocking, Nouveau Remains Behind NVIDIA's Proprietary Linux Driver
  2. The Power Consumption & Efficiency Of Open-Source GPU Drivers
  3. AMD R600g/RadeonSI Performance On Linux 3.16 With Mesa 10.3-devel
  4. Intel Pentium G3258 On Linux
Latest Linux Articles
  1. Nouveau vs. Radeon vs. Intel Tests On Linux 3.16, Mesa 10.3-devel
  2. KVM Benchmarks On Ubuntu 14.10
  3. X.Org Server 1.16 Officially Released With Terrific Features
  4. Ubuntu With Linux 3.16 Smashes OS X 10.9.4 On The MacBook Air
Latest Linux News
  1. GCC As A Just-In Time Compiler Is An Interesting Project
  2. Age Of Wonders III Is Still Being Ported To Linux
  3. Git 2.1 To Further Mainline Windows Support Patches
  4. Debian 8.0 Jessie Is Settling For Linux 3.16
  5. Meson: A Next-Gen Build System Showing Promise
  6. Linux 3.16-rc7 Calms Things Down For The Linux 3.16 Kernel
  7. Open-Source AMD Users Report Hawaii GPU Acceleration Is Working
  8. Linus Torvalds On GCC 4.9: Pure & Utter Crap
  9. Cauldron 2014: GCC & LLVM Will Look To Collaborate More
  10. GCC Receives ACM Programming Languages Software Award
Latest Forum Discussions
  1. Porting Mesa to the Playstation 2
  2. Updated and Optimized Ubuntu Free Graphics Drivers
  3. ASRock AM1H-ITX: One Of The Best AM1 Mini-ITX Motherboards
  4. Debian + radeonsi
  5. Open-source drivers on ATI R7 260X
  6. Table test
  7. How To Setup Radeon DPM On Ubuntu Linux
  8. New build, first Linux PC, what could go wrong? ;)