Testing Radeon DPM Using Sysfs/Debugfs
For those looking to test out the long-awaited Radeon dynamic power management support within the Linux 3.11 kernel, here's some information on the new debugfs and sysfs interfaces for dealing with this "DPM" feature.
The Radeon updates for the Linux 3.11 kernel are very exciting as the GPU clock speeds and voltages can dynamically adjust based upon load. This leads to power-savings when idling, especially for battery-backed systems, and also to greater performance on newer hardware by being able to up-clock the GPU from its boot speeds. In this next kernel release there is also Radeon HD 8000 "Sea Islands" open-source GPU support in early form.
The dynamic power management support has already seen code revisions and bug-fixes prior to merging to mainline. With these revisions have come new debugfs/sysfs entries for dealing with the dynamic power management levels.
For those looking for descriptions on these new sysfs and debugfs entries for monitoring and toggling dynamic power management states, AMD's Alex Deucher has written a new blog post that describes these new tunable options.
As a reminder, with the Linux 3.11 kernel the DPM support is disabled by default and the kernel must be booted with the radeon.dpm=1 kernel module parameter. Once the DPM support is well-tested and proven to be reliable, it will be enabled by default.
For those seeking additional information on Radeon DPM within this open-source Linux driver, AMD's Alex Deucher and John Bridgman have been answering Phoronix reader questions within this forum thread, among other Phoronix threads.
As soon as Linux 3.11-rc1 is out there with this support, Radeon DPM benchmarks will begin at Phoronix.
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