[linuxkernelnewbies] nouveau Wiki - OProfile

[Peter Teoh]

http://nouveau.freedesktop.org/wiki/OProfile OProfile Why OProfile? Sometimes you want to get an idea were bottlenecks lie, and oprofile is ideal for that. It's a statistical profiler for linux. It requires kernel support (CONFIG_OPROFILE). Basic howto Install oprofile and make sure your kernel supports it. Setting kernel image. Yes, this is really vmlinux, not bzImage. You may find it in your kernel source tree after compiling. opcontrol --vmlinux=/path/to/vmlinux or if you do not have it opcontrol --no-vmlinux Setting call graph depth (optional, for x86 and PPC only) opcontrol --callgraph=6 Delete old oprofile results opcontrol --reset Start profiling opcontrol --start Do the thing you wanted to profile. Make sure all profile data gets into files. opcontrol --dump Stop profiling. opcontrol --stop Various commands to see the results: opreport opreport -l opreport -l /path/to/specific/module/or/application opreport --callgraph Unload oprofile opcontrol --deinit Alternatively, you can use a modified version of Carl Worth's oprofile script that can be found [here:http://cworth.org/bin/profile]. Change the paths to match the ones of your system. Notes The callgraph function can provide some hints were function calls are coming from, you just have to get familiar with them before you understand them. Please be aware that optimisation leads to inlining of functions and this affects profiling just as it affects debugging. You'll need to request a callgraph depth for this to work. If you want to get kernel symbols, you'll need to add the path to vmlinux, this is not the compressed image. It can usually be found in /usr/src/linux/vmlinux if you compiled your own kernel.