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4. Debugging and benchmarking

4.1. How do you put a breakpoint in the dynamically loaded modules?

You need xfree86-gdb, which is a version of gdb modified to understand the module binary format that XFree86 uses in addition to the standard elf/coff binary formats.

Example 1. Using xfree86-gdb

modules mach64_drv.o mach64_dri.o
after starting the debugger to load symbols, etc.

xfree86-gdb is freely available from here.

4.2. How do I do benchmarking with Unreal Tournament?

Start a practive level. Type timedemo 1 in the console or in alternative select the "TimeDemo Statistic" menu entry under the "Tools" section.

You should see two numbers in white text on the right side of the screen showing the average framerate (Avg) and the number of frame rates in the last second (Last Sec). If this doesn't work check whether the stats get reported in your ~/.loki/ut/System/UnrealTournament.log file.

4.3. Is there any way for us to detect which features are implemented with hardware support for a given driver?

OpenGL doesn't have such a query. This is a potential problem with any OpenGL implementation. The real question one wants answered is "is this feature or GL state combination fast enough for my needs?". Whether a feature is implemented in hardware or software isn't always consistant with that question.

You might consider implementing a benchmark function to test the speed during start-up and making a decision depending on the result. The info could be cached in a file keyed by GL_RENDERER.

Check isfast

4.4. Which OpenGL benchmarking program can I use to test and compare various facets of the performance of graphics cards?


You can use OpenGL games such as Quake 3, Unreal Tournament, etc.


SPECviewperf is a portable OpenGL performance benchmark program written in C providing a vast amount of flexibility in benchmarking OpenGL performance.


SPECglperf is an executable toolkit that measures the performance of OpenGL 2D and 3D graphics operations. These operations are low-level primitives (points, lines, triangles, pixels, etc.) rather than entire models.


glean is a suite of tools for evaluating the quality of an OpenGL implementation and diagnosing any problems that are discovered. It also has the ability to compare two OpenGL implementations and highlight the differences between them.


machtest is a thorough benchmark for graphics cards. It has literary thousands of command line options, is easily extensible and it can produce machine readable output.

Mesa demos

4.5. How should I report bugs?

Please submit bugs through the bug tracking system in SourceForge. It`s the only way we can keep track of all of them. Write up one problem in each bug report. It`s best if you can create a small example that shows what you think is the problem.

For those who really want to be Open Source heros -- you can create a test for the bug under glean. The intention would be to run glean quite often, so any functionality you can verify there, is much less likely to reappear in a broken form at some random time in the future.