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?highlight=cost%20centre#rts-flag--pa and https://gitlab.haskell.org/ghc/ghc/-/blob/cf47b96f8b8100d9f9ad1b8121cbfb65fd7eaf2a/rts/ProfilerReport.c#L124 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.hollenb...@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 >
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