Callgrind: Profile a specific part of my code

Question

I\'m trying to profile (with Callgrind) a specific part of my code by removing noise and computation that I don\'t care about. Here is an example of what I want to do:

Answer 1

The toggle-collect option is very picky in how you specify the method to use as trigger. You actually need to specify its argument list as well, and even the whitespace needs to match! Use the method name exactly as it appears in the callgrind output. For instance, I am using this invokation:

$ valgrind 
    --tool=callgrind 
    --collect-atstart=no 
    "--toggle-collect=ctrl_simulate(float, int)"
    ./swaag

Please observe:

• The double quotes around the option.
• The argument list including parentheses.
• The whitespace after the comma character.

Answer 2

I finally managed to solve this issue... This was a config issue:

I kept the code

for (int i=0; i<maxSample; ++i) {
    //Prepare data to be processed...
    CALLGRIND_TOGGLE_COLLECT;
    //Method to be profiled with these data
    CALLGRIND_TOGGLE_COLLECT;
    //Post operation on the data
}
CALLGRIND_DUMP_STATS;

But ran the callgrind with --collect-atstart=no (and without the --instr-atstart=no!!!) and it worked perfectly, in a reasonable time (~1min).

The issue with START/STOP instrumentation was that callgrind dumps a file (callgrind.out.#number) at each iteration (each STOP) thus it was really really slow... (after 5min I had only 5000 runs for a 300 000 iterations benchmark... unsuitable for a regression test).