For months now he's had a solid understanding of how NVIDIA's performance counters operate and has been working towards exposing them in a NVPerfKit-like open-source manner and exposing them to OpenGL developers. Samuel's latest update revealed his MP counter work was up to a prototype stage while today he has a new blog post concerning the approaches to exposing the performance counters in Nouveau.
The post focuses on the methods for exposing NVIDIA's global counters engine by using either a "all user-space" or "all kernel-space" approach. Samuel has worked up code for both versions and made the necessary changes to his branched versions of the Nouveau DRM, libdrm, and Mesa.
While the answer of what approach is better is still up in discussion, Pitoiset is leaning towards the kernel-based approach as it's more elegant and future-proof. Samuel hopes this performance counter code will be ready for merging in time for the Linux 3.19 kernel in the months ahead. Read more on Samuel's blog.