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. Acer B286HK: A 28-inch UHD LED 4K Monitor For As Low As $350
  2. Intel Xeon E5-1680 v3 & E5-2687W v3 Compared To The Core i7 5960X On Linux
  3. Intel 120GB 530 Series SSD Linux Performance
  4. Btrfs/EXT4/XFS/F2FS RAID 0/1/5/6/10 Linux Benchmarks On Four SSDs
Latest Linux Articles
  1. Mesa Git Yields Performance Improvements For Newer AMD GPUs
  2. Apple OS X 10.10 vs. Ubuntu 14.10 Performance
  3. Mesa 10.5-devel Brings Some Intel Haswell HD Graphics Changes Over Mesa 10.3
  4. NVIDIA vs. Nouveau Drivers With Linux 3.18 + Mesa 10.4-devel
Latest Linux News
  1. AMD Richland APU Support Added To Coreboot
  2. 2014 Holiday Shopping Reminder, Happy Thanksgiving
  3. Python 3 Support Added To The GNOME Shell
  4. ReactOS Lands Its New Explorer Shell
  5. Weston's IVI Shell Sees New Version
  6. IMP Launches As Another Open-Source Computer Attempt
  7. Git 2.2.0 Released With 550+ Changes
  8. GNOME 3.15.2 Released
  9. Quantum OS Aims For A Linux Desktop With QML, Wayland & Material Design
  10. New Open-Source, Linux Benchmarks To Feast On
Latest Forum Discussions
  1. Updated and Optimized Ubuntu Free Graphics Drivers
  2. Hurrican SDL Port
  3. Roadmap to Catalyst 14.10 ?
  4. how to configure module phoromatic ?
  5. PulseAudio 6.0 Is Coming & Other Linux Audio Plans For The Future
  6. Debian Developer Resigns From The Systemd Maintainership Team
  7. Cant get working Kaveri APU - A10-7850k
  8. Script for Fan Speed Control