Will Nouveau Driver Impact Ubuntu 12.04's Battery?
Last night I shared a preview of the best and worst case examples of power consumption on Ubuntu 12.04 LTS. In a good case, for newer PC hardware, an Intel notebook was going through nearly 40% less power while idling on Ubuntu 12.04 compared to Ubuntu 11.10 and earlier releases. However, for older PC hardware, Precise Pangolin's power consumption was up sharply -- 30% higher than when the Intel "Dothan" was in its prime.
The results in full of a wide-range of Ubuntu 12.04 power consumption tests will be published next week, but for old hardware you're really better off not upgrading to Ubuntu 12.04. Anyhow, as another quick test carried out was to see what the Nouveau vs. NVIDIA official driver power consumption difference is under this forthcoming Ubuntu Long-Term Support (LTS) release.
Ubuntu 12.04 is shipping with the Linux 3.2 kernel and Mesa 8.0 by default with the Nouveau Gallium3D driver enabled -- a change they first made in Ubuntu 11.10 to have open-source NVIDIA OpenGL acceleration "out of the box" for users. For desktop hardware from both ATI/AMD Radeon and NVIDIA GeForce GPUs, earlier results have shown the proprietary drivers to lead to greater power efficiency since those official drivers support a range of features not found within the open-source drivers and have been much better tuned by engineers at the respective companies.
[drm] nouveau 0000:01:00.0: 3 available performance level(s)Being stuck to a lowered performance state by default and not dynamically changing states based upon graphics load, this did lead to more favorable power consumption results for the Nouveau driver when experiencing OpenGL load.
[drm] nouveau 0000:01:00.0: 0: core 135MHz shader 270MHz memory 135MHz timing 2 voltage 800mV
[drm] nouveau 0000:01:00.0: 1: core 405MHz shader 810MHz memory 324MHz timing 1 voltage 850mV
[drm] nouveau 0000:01:00.0: 3: core 550MHz shader 1210MHz memory 790MHz timing 0 voltage 930mV
[drm] nouveau 0000:01:00.0: c: core 405MHz shader 810MHz memory 324MHz voltage 930mV
So while the open-source Nouveau driver can't exactly compete with the binary NVIDIA Linux driver "out of the box" in performance terms, at least it's not burning through excessive amounts of power with the GT216-based Quadro mobile graphics processor. These benchmarks are available on OpenBenchmarking.org via 1203307-SU-NVIDIAQUA48.
For those wanting to explore Nouveau re-clocking, see Nouveau Reclocking: Buggy, But Can Boost Performance. New Nouveau driver benchmarks under different conditions are forthcoming now that the Nouveau DRM/KMS driver has left the staging area of the kernel for Linux 3.4. The Nouveau developers also continue to work on some other power optimizations too.