In the forum discussion surrounding the significant underlying Nouveau driver changes found in Linux 3.7, Nouveau's Martin Peres wrote, "No luck for this kernel, but I think I'm not that far from delivering good reclocking support for the nv50 family. Maybe next kernel?" His comments were in response to a Phoronix reader asking about dynamic re-clocking and voltage changes.
Martin Peres is one of the Nouveau developers that has been heavily focusing on power management and re-clocking for this reverse-engineered NVIDIA Linux driver. He's also the one that worked on the fan control support for NVIDIA graphics cards that is now found in the Linux 3.7 kernel DRM.
There isn't yet this "good reclocking support" living in the Nouveau DRM development tree for -next yet, but it's promising to see that Martin hopes it will be ready for the next kernel (Linux 3.8). The NV50 series is comprised of the GeForce 8 and GeForce 9 graphics products. Unfortunately, it will still likely be a while before there is good Nouveau driver re-clocking support for the more recent GeForce 400/500 "Fermi" and GeForce 600 "Kepler" graphics cards.
Also coming up today is another short article looking at the Nouveau vs. NVIDIA performance and a re-clocking snafu.
Re-clocking support is critical for not only better power management to drop the operating frequencies when the GPU is not busy, but also for reaching maximum performance. At the moment the GPU core, memory, and shader clocks with the Nouveau driver are running at whatever speed they were set at by the video BIOS when the system was booting. On modern hardware, these boot core/vRAM/shader clocks are often much lower than their rated frequencies to run at and the frequencies the NVIDIA binary driver uses when the hardware is under load. There is limited (and often buggy) re-clocking support for some Nouveau configurations right now as covered by Nouveau Reclocking: Buggy, But Can Boost Performance.