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 New Patch For Radeon DRM Power Savings

AMD

Published on 21 November 2009 09:35 AM EST
Written by Michael Larabel in AMD
35 Comments

While OpenGL acceleration and GPU-assisted video playback are often most viewed as the areas that are severely lacking for the open-source Linux graphics drivers in comparison to what the binary-only ATI/NVIDIA drivers offer, another area that has not yet caught up to speed with the binary competition is power management. For years (going back to 2005) AMD has implemented PowerPlay support in their fglrx driver for dynamically clocking the GPU and memory clocks along with adjusting the voltages accordingly, based upon the user's input and then later generations of PowerPlay are more dynamic in nature. NVIDIA also supports their PowerMizer technology on Linux for dynamically clocking their GPUs/memory and voltages based upon the graphics processor's load.

When it comes to the open-source ATI power management efforts, Red Hat's Matthew Garrett has been working on dynamic down-clocking through AtomBIOS, dynamic clocks support was added to the ATI driver for R500+ GPUs to support dynamic clock-gating and static power management, force low power mode options, and various other techniques are being worked on to conserve power like frame-buffer compression, shutting down PLLs, LVDS re-clocking, and more.

In September of this year there was then a set of patches that were published to introduce reading clock values, storing power management states, setting new power states, and reading min/max clock values for the ATI kernel mode-setting driver. This work was done by Rafał Miłecki. This initial work didn't do too much beyond laying the foundation for KMS power management support in the ATI stack, but it would automatically down-clock the GPU if the connected display was signaled off via DPMS. This morning though Rafał has published a new ATI power management patch for its DRM.

This newest patch adds dynamic engine re-clocking based upon the GPU's work load. His patch calculates the number of commands not yet processed by the GPU and uses that to judge the GPU's load. If all commands are processed, the GPU is then down-clocked with a 200ms delay, but if there are unprocessed commands, the GPU will re-up its clocks. Rafał's initial tests have yielded that this works for keeping the GPUs clocked lower (and thus conserving power) when just within KDE or glxgears, but when firing up a game like OpenArena the engine will re-clock itself to its performance state. No major performance drops were noted with this dynamic clocking patch.

This patch, however, is not 100% ideal yet as it does not deal with changing the frequency of the memory (waiting for IRQ support on that as it's important to not re-clock the memory when it's busy), voltages aren't being changed between states (it's on his TODO list for "later"), and there are also a few horizontal black lines that appear on the screen when the GPU engine is being re-clocked. This patch could also be more aggressive in determining its load and other factors.

However, for those interested in playing with this preliminary patch, it can be found on the dri-devel mailing list.

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. Kubuntu 15.04 Is Turning Out Quite Nice, Good Way To Try Out The Latest KDE
  2. 5-Way Linux Distribution Comparison On The Core i3 NUC
  3. OCZ ARC 100 Linux SSD Benchmarks
  4. Lenovo ThinkPad X1 Carbon Works Great As A Linux Ultrabook
  5. Transcend SSD370 256GB
  6. Linux 3.19 File-System Tests Of EXT4, Btrfs, XFS & F2FS
Latest Linux News
  1. Open-Source .NET On Linux Continues Maturing
  2. Features Coming For The Imminent Xfce 4.12 Release
  3. Canonical's Latest Demo Of Ubuntu Unity 8 Convergence In Action
  4. The Quest For Decent, Low-Priced Server Cases & Racks/Cabinets
  5. Mesa 10.5 Is In Ubuntu 15.04 For The Latest Open-Source GPU Drivers
  6. ALSA 1.0.29 Released
  7. Ubuntu 15.04 Beta Released, Ubuntu MATE Made Official
  8. Coreboot Developer: Purism Doesn't Deliver On Libre Firmware
  9. LLVM 3.6 & Clang 3.6 Deliver More Features, Complete C++14 Support
  10. The Most Popular Open-Source Linux Benchmarks
Most Viewed News This Week
  1. Linux 4.0-RC1 Tagged, Linux 4.0 Will Bring Many Notable Improvements
  2. Screenshots Of The GNOME 3.16 Changes
  3. Linux 4.0 Doesn't Have The Weirdest Codename
  4. Mir Now Depends Upon C++14
  5. More Proof That Allwinner Is Violating The GPL
  6. GNOME 3.16 Beta Brings Wayland-Based Log-in Screen
  7. LLVM Clang Compiling The Linux Kernel Is A Big Topic For 2015
  8. Canonical Comes Up With Its Own FUSE Filesystem For Linux Containers
%%CLICK_URL_UNESC%%