Hi Celeste, It looks like by default only cost centers that account for at least 1% of either allocations or time are shown. But all cost centers are shown when the -pa flag is passed. See: https://downloads.haskell.org/ghc/latest/docs/users_guide/profiling.html?hig... and https://gitlab.haskell.org/ghc/ghc/-/blob/cf47b96f8b8100d9f9ad1b8121cbfb65fd... If you are processing these reports, it might be worth checking out the eventlog interface via the ghc-events library (if you haven't already). Cheers, Teo On Tue, Jul 30, 2024 at 3:58 PM Celeste Hollenbeck < celeste.hollenbeck@gmail.com> wrote:

Hi GHC Team,

I have a question for a research project. I'm looking at GHC's profiler, and the documentation says a profiling report displays "a break-down by cost centre of the most costly functions in the program". Here's an example of the report that I'm talking about:

MAIN MAIN 102 0 0.0 0.0 100.0 100.0 CAF GHC.IO.Handle.FD 128 0 0.0 0.0 0.0 0.0 CAF GHC.IO.Encoding.Iconv 120 0 0.0 0.0 0.0 0.0 CAF GHC.Conc.Signal 110 0 0.0 0.0 0.0 0.0 CAF Main 108 0 0.0 0.0 100.0 100.0 main Main 204 1 0.0 0.0 100.0 100.0 fib Main 205 2692537 100.0 100.0 100.0 100.0

This example is under Section 8.1 of the GHC User's Guide

https://downloads.haskell.org/ghc/latest/docs/users_guide/profiling.html#:~:text=GHC's%20profiling%20system%20assigns%20costs,to%20the%20enclosing%20cost%20centre.

It looks like the numbers often add up to less than 100% for the %time, but I don't see any documentation on a threshold for what makes a cost centre "costly"—so I assume that "costly" means that it takes up any time whatsoever, and any cost centres that take up any time at all are included in the report? So perhaps the numbers under %time don't add up to 100% all the time because of rounding error or perhaps garbage collection? Or something else that is not profiled?

Is that correct?

Thanks,

Celeste _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs