Lack of decent profiling is a major problem for making our operating system fast. By far the most effective of profiling is sampling profile with callgraph information. Soeren's comment from March: http://lwn.net/Articles/380582/ Basically summarizes the situation, and as far as I know nothing has changed ... with default compilation options, getting callgraph profiling on x86_64 really requires a DWARF unwinder in the kernel. Which seems unlikely to happen. As a developer, your options for profiling are: - Recompile everything you care about profiling with -fno-omit-frame-pointer instead of using system packages. - Switch to i386 Even if the second was reasonable to ask of developers, it also makes it really hard to help users with performance problems if they have to reinstall their system to give you a profile. So, I'd like to bring up the possibility of switching to compiling our packages with -fno-omit-frame-pointer for x86_64. As Soeren says, x86_64 isn't register starved, so the performance penalty shouldn't be huge. But I have no idea if it's 0.5% or 5%. What aspects of performance do we care about? How would we measure the performance impact of changing compilation flags? What is the acceptable slowdown? - Owen (One downside of any slowdown is that if we take a 1% hit and do performance work that makes the system 10% faster, then we look bad by comparison with other Linux distributions who get the advantages of the performance work but don't take the 1% hit. Still, we should do what has the biggest net gain for our users, right?) -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel
