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

Linux 3.5 Kernel Power Regression Spotted

Linux Kernel

Published on 31 July 2012 06:33 PM EDT
Written by Michael Larabel in Linux Kernel
7 Comments

Following yesterday's news of a massive power regression within the Linux 3.5 kernel, James Bottomley has uncovered the kernel commit causing excessive power usage.

The cause of this latest Linux kernel power regression in 3.5 compared to Linux 3.4 is 2911a35b2e4eb87ec48d03aeb11f019e51ae3c0d, or more easily it's "drm/i915: use semaphores for the display plane." This commit to the Intel DRM graphics driver for using semaphores for the display plane is what's causing select hardware to burn through much more power than its predecessor.

To the contrary, the commit message for the i915 driver commit actually advertises this kernel change as possibly causing power and performance improvements. "In theory this will have performance and power improvements. Performance because we don't need to stall when the scanout BO is busy, and power because we don't have to stall when the BO is busy (and the ring can even go to sleep if the HW supports it)."

Bottomley mentioned this problematic commit in this mailing list message and now Intel developers are working on figuring out a fix for this non-trivial commit.

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 Articles & Reviews
  1. Khronos Group Announces Vulkan, OpenCL 2.1, SPIR-V
  2. Samsung 850 EVO SSD Linux Benchmarks
  3. Kubuntu 15.04 Is Turning Out Quite Nice, Good Way To Try Out The Latest KDE
  4. 5-Way Linux Distribution Comparison On The Core i3 NUC
  5. OCZ ARC 100 Linux SSD Benchmarks
  6. Lenovo ThinkPad X1 Carbon Works Great As A Linux Ultrabook
Latest Linux News
  1. Gitorious Gets Acquired By GitLab
  2. Unity 5.0 Brings PhysX 3.3, WebGL Preview, Animation System Work
  3. Linux 4.0-rc2 Kernel Released After Delay Due To Intel DRM Driver
  4. Linux 3.19 Officially Lands For Ubuntu 15.04
  5. Clutter Now Supports Quad-Buffer Stereo Displays, Mir Backend
  6. Pricing Details On The Alleged MJ Ubuntu Tablet Design
  7. Understanding The Linux Kernel's BPF In-Kernel Virtual Machine
  8. Another Software Patent That Should Be Tossed Out
  9. Imagination Already Has A Vulkan Driver In The Works For PowerVR GPUs
  10. A Provisional Specification To SPIR-V
Most Viewed News This Week
  1. More Proof That Allwinner Is Violating The GPL
  2. The Tremendous Features Of Fedora 22
  3. Krita 2.9 Released, Their Biggest Release Ever
  4. A Single UEFI Executable With The Linux Kernel, Initrd & Command Line
  5. LLVM 3.6 & Clang 3.6 Deliver More Features, Complete C++14 Support
  6. Firefox 36 Brings Full HTTP/2 Support
  7. Xfce 4.12 Released After Nearly Three Years Of Work
  8. ALSA 1.0.29 Released
%%CLICK_URL_UNESC%%