Importing from Haskell

GHC provides built in profiling support that can export a JSON file. In order to do this you need to compile your executable with profiling support and then pass the -pj RTS flag to the executable.

This will produce a my-binary.prof file in the current directory which you can import into speedscope.

Using GHC

See the GHC manual page on profiling for more extensive information on the command line flags available.

$ ghc -prof -fprof-auto -rtsopts Main.hs
$ ./Main +RTS -pj -RTS

Using Stack

With executables

$ stack build --profile
$ stack exec -- my-executable +RTS -pj -RTS

With tests

stack test --profile --test-arguments "+RTS -pj -RTS"