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 Comment On The Linux 2.6.38 Power Regression

Hardware

Published on 27 June 2011 01:10 PM EDT
Written by Michael Larabel in Hardware
21 Comments

Jesse Barnes, the maintainer of the PCI subsystem for the Linux kernel and one of the developers who signed-off on the patch that I discovered is causing the major Linux 2.6.38 kernel power regression, has commented on the matter.

When Jesse isn't working on the Intel Linux graphics driver stack as part of Intel's Open-Source Technology Center, he's working on the Linux PCI subsystem. At the time the article was published last night that details the 2.6.38 power regression commit, there wasn't any comment from the kernel developers due to being unable to reach them over the weekend.

This morning Jesse wrote, "the behavior unfortunately sounds correct (or at least intended)." He confirmed that they just use a BIOS flag to determine whether to manage the PCI Express link state, since if both the kernel and BIOS are attempting to manage the PCI-E link, a hang can result or the device failing.

With this behavioral change, many mobile users are experiencing significant decreases in their battery life as the power consumption rate can go up easily over 10% -- with reports as high as 40%+ differences. Jesse believes that Microsoft must have additional checks in place when determining whether Windows should handle Active-State Power Management or not. Windows hardware drivers might also be responsible for enabling ASPM where supported, but on the Linux side there's only a couple kernel drivers banging the ASPM bit.

There isn't any easy "solution" to improve this situation beyond affected users forcing the PCI-E Active-State Power Management using the pcie_aspm=force kernel command line option. Jesse thinks that more Linux drivers will end up needing to set the ASPM bits directly as a long-term solution. There's just too many hardware devices that don't properly support the ASPM power-saving modes.

The only alternative would be to create a big white-list of supported devices, but that comes down to being effectively the same large task as just having the driver set the appropriate bit. So there won't be any magic fix in the Linux 3.0 kernel nor will there likely be any major change in the Linux 3.1 kernel without suddenly a bunch of drivers handling the Active-State Power Management bit. For now, mobile users just need to know to force the PCI-E ASPM support if needed to maximize the Linux battery life.

There's still a few more kernel power regressions I'm working on and some other Linux power tests. Tomorrow is a look at the Catalyst vs. Radeon DRM/KMS power consumption in different power management modes.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Linux Hardware Reviews
  1. AMD R600g/RadeonSI Performance On Linux 3.16 With Mesa 10.3-devel
  2. Intel Pentium G3258 On Linux
  3. SilverStone Precision PS10
  4. ASRock Z97 Extreme6
Latest Linux Articles
  1. KVM Benchmarks On Ubuntu 14.10
  2. X.Org Server 1.16 Officially Released With Terrific Features
  3. Ubuntu With Linux 3.16 Smashes OS X 10.9.4 On The MacBook Air
  4. Preview: Benchmarking CentOS 7.0 & Scientific Linux 7.0
Latest Linux News
  1. Unigine Develops City Traffic System, A Driving Simulator
  2. Intel 3.0 X.Org Driver Still Baking, New Development Release
  3. Eric Anholt Makes Progress With Broadcom VC4 Graphics Driver
  4. Intel Is Getting Very Close To OpenGL 4.0/4.1/4.2 Mesa Support
  5. Valve Is Still Hiring For SteamOS, Linux Work
  6. Users Warned About Possible Regressions With DRI3
  7. GNOME Shell Gets Wayland HiDPI Fonts, Mutter Gets Touch Gestures
  8. BPTC Texture Compression Comes To Nouveau After Intel's Work
  9. Development Continues For Supporting EXT4 On NVDIMMs
  10. Libinput 0.5 Improves Pointer Acceleration, Adds A Configuration API
Latest Forum Discussions
  1. Updated and Optimized Ubuntu Free Graphics Drivers
  2. Radeon related kernel bug??
  3. AMD Publishes Open-Source Linux HSA Kernel Driver
  4. Next-Gen OpenGL To Be Announced Next Month
  5. Open-Source Radeon Performance Boosted By Linux 3.16
  6. Remote gui not accessible in Phoronix Test Suite 5.2
  7. AMD "Hawaii" Open-Source GPU Acceleration Still Not Working Right
  8. In Road To Qt, Audacious Switches From GTK3 Back To GTK2