[Haskell-cafe] Profiling/cost centre question

[Sebastian Reese]

Hi there,

I mailed to this list in May  
(http://www.haskell.org/pipermail/haskell-cafe/2009-May/062126.html)  
with no answer at all. So I wrote a smaller program to demonstrate my  
problem/question. Maybe now someone can help me now.

I wrote a small program that does nothing but listening on a TCP port.
After connection is done it simply terminates.

#> cat Test.hs
module Main where

import Network

main :: IO ()
main =
   (do
   servSock <- {-# SCC "cc1" #-}listenOn . PortNumber $ 10000
   (handle, host, port) <- {-# SCC "cc2" #-}accept servSock
   return ()
   )`catch` (putStrLn . show)
#>

I compile, run (connection from elsewhere, so program terminates) and  
watch the .prof output

#> ghc --make -threaded -O2 -prof -caf-all -auto-all Test.hs
Linking Test ...
#> ./Test +RTS -p
#> cat Test.prof
         Thu Jun 18 12:24 2009 Time and Allocation Profiling Report  (Final)

            Test +RTS -p -RTS

         total time  =        0.32 secs   (16 ticks @ 20 ms)
         total alloc =      32,384 bytes  (excludes profiling overheads)

COST CENTRE                    MODULE               %time %alloc

MAIN                           MAIN                 100.0    7.8
CAF                            GHC.Conc               0.0    4.0
CAF                            GHC.Handle             0.0   26.8
cc1                            Main                   0.0    3.8
cc2                             Main                   0.0   55.8

  ... snip ...

#>

My actual question is, where does the 100% individual time from MAIN  
come from, how can I debug that in other programs and where does this  
MAIN cost centre come from?

thanks for your help
Sebastian

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