It's long been known, especially since Valve's been talking about it, that OpenGL debugging support could be vastly improved for Linux. There's much better support found on Windows with different Windows-only OpenGL debugging programs and more advanced debugging support found within the proprietary AMD and NVIDIA graphics drivers. It's easy there to detect bottlenecks in your game/application/driver, easier to find problematic code-paths, etc. Ian Romanick is calling on Linux developers to change the situation.
He's hoping for new kernel interfaces and other changes to allow for finer-grained data about the execution of commands on the GPU and system level data with semantic information to help debugging. While open-source driver support is their main focus, he hopes the interfaces will also work for the closed-source graphics drivers too.
Ian laid out the plans for his LPC talk tomorrow in this blog post.
For OpenGL/graphics debugging on Linux among the current user-space solutions are AMD's gDebugger as a popular solution, the popular open-source APITrace, and others. The Phoronix Test Suite also has various performance monitoring characteristics built in too that can be exposed for any test profile.
Besides Valve's interest in better graphics analyzing and debugging, they also feel Linux is lacking when it comes to debugging support overall. Valve is heavily interested (and investing in) LLVM's LLDB and they are also working on a new Linux game debugger in cooperation with RAD Games Tools. Gabe Newell also reaffirmed Linux's debugging shortcomings at his Linux gaming keynote this week from LinuxCon.