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 Benchmarking Platform
Phoromatic Test Orchestration

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 Articles & Reviews
  1. Ubuntu 15.04 Offers Faster OpenGL For AMD Radeon GPUs On Open-Source
  2. Ubuntu 15.04 Brings Some Graphics Performance Improvements For Intel Haswell
  3. Sub-$20 802.11n USB WiFi Adapter That's Linux Friendly
  4. The Lenovo T450s Is Working Beautifully With Linux
  5. Linux 4.0 SSD EXT4 / Btrfs / XFS / F2FS Benchmarks
  6. Linux 4.0 Hard Drive Comparison With Six File-Systems
Latest Linux News
  1. Phoronix Server Migration
  2. GCC 5.2 Will Come In Two To Three Months
  3. AMD FP3 Motherboard Ported To Coreboot
  4. The Difference In Optimizations Between NIR & GLSL
  5. OpenMandriva Lx 3 Alpha: Adds UEFI Support, Defaults To LXQt
  6. Systemd Kills Off Shutdownd
  7. There's Now More Than 1,100 Games On Steam For Linux
  8. Btrfs In Linux 4.1 Has Fixes For File-Systems Of 20 Terabytes & Up
  9. Microsoft's CoreCLR Now Works On FreeBSD
  10. Unigine 2.0 Beta 2 Brings PBR, SSR, Kinect 2 Support
Most Viewed News This Week
  1. AMD Releases New "AMDGPU" Linux Kernel Driver & Mesa Support
  2. Ubuntu's Desktop-Next Switching From .DEBs To Snappy
  3. My Favorite Computer Desk Of The Past Decade For Less Than $100
  4. AMD Open-Sources "Addrlib" From Catalyst
  5. Library Operating System (LibOS) For Linux Still Being Pursued
  6. Debian 8.0 Jessie Is Ready For Release This Weekend
  7. GIMP's Porting To GTK3 Continues
  8. Features Thus Far For The Linux 4.1 Kernel