Profiling executable with criterion

Question

I need to profile a large number of haskell executables, hopefully in parallel. I was able to get the clock time with measure and measTime from the Criterion library, but couldn't get measCpuTime or any GC report to work (measCpuTime returns a time that's impossibly short). The code looks like:

buildProj :: FilePath -> IO ExitCode
buildProj projDir = system $ "cd " ++ projDir ++ "; cabal sandbox init; cabal configure; cabal build"

-- Time a project
instance NFData ExitCode
  where 
    rnf ExitSuccess = ()
    rnf (ExitFailure _) = ()


benchmark :: FilePath -> Int64 -> IO Double
benchmark projDir runs =  do  
  let runProj = "./" ++ projDir ++ "/dist/build/" ++ projDir ++ "/" ++ projDir ++ "> /dev/null"
  exit <- timeout 17000000 $ system runProj -- TODO hardcode timeout
  case exit of
       Just ExitSuccess     -> do {(m, _) <- measure (nfIO $ system runProj) runs; 
                              return $! measTime m}
       Just (ExitFailure _) -> return 100 
       Nothing              -> return 100

In short, I'm running the executables with System.Process.system as an IO action and I've declared ExitCode as NFData in order to get nfIO to work. What have I done wrong? Are there better tools to do the task?

The file's here if you want to play with it.

Well your child process's CPU time is not your CPU time, so no surprise that `measCpuTime` doesn't do what you want. Not sure how to measure the child process's CPU time, though it is obviously possible since `time` does it. — Reid Barton, Oct 12 '15 at 20:11
I'm thinking to use the GHC API to do the profile, but not sure where to start looking — rem, Oct 13 '15 at 20:57

score 0 · Answer 1 · edited May 23 '17 at 12:23

I took a look at this SO question and got some ideas. First note that criterion uses cbits to enable system-dependent cpu time functions. Let's pretend you're on unix. The simplest thing to do is to directly read from /proc/PID/stat/cutime at the start and end of your runs and take the difference. Beyond that, you can actually use the c code provided in that question, link it in yourself as a foreign import, and then call that directly from your own code.

Profiling executable with criterion

1 Answers1