how can i use perf to profile my code?

Question

I'm trying to use "perf" to see what's using all the CPU in my C++ program on Linux. I want to attach to a running process and get a list of symbols or line numbers that I can then go look at to optimize.

Answer 1

To attach to a process and see live updates of hotspots:

perf top -p $(pidof yourapp)

To attach to a process, then analyse it for later evaluation, do:

perf record -p $(pidof yourapp)

And later:

perf report

For both, top and record, you can add --call-graph dwarf for dwarf-based callgraphs.

Note that you should compile your application with something like -O2 -g to get optimizations and debug symbols, otherwise you won't know functions names, files, line numbers etc. pp.