[GHC] #13492: -p option report much less time than actual on high intensity of FFI calls application

[GHC]

#13492: -p option report much less time than actual on high intensity of FFI calls
application
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           Reporter:  varosi         |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Profiling      |           Version:  8.0.2
           Keywords:                 |  Operating System:  Windows
       Architecture:  x86_64         |   Type of failure:  Debugging
  (amd64)                            |  information is incorrect
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Proprietary application is ran on 44 cores (88 with HT) machine (same
 problem on 12 core). It is Haskell between wxHaskell (wxWidgets for UI)
 and C API. It is doing FFI calls most of the time. Calls are not so many,
 but possibly not so fast. I'm trying to profile where is the problem, in
 which calls. But very strange behaviour is there. "total time" of
 application that is running 30secs to 1min is showing 0.33secs. Even MAIN
 function is not 100%.

 Please, see first part of .prof file:

         Tue Mar 28 15:38 2017 Time and Allocation Profiling Report
 (Final)

            app.exe +RTS -N -A40m -qb0 -p -RTS

         total time  =        0.33 secs   (325 ticks @ 1000 us, 1
 processor)
         total alloc =  86,317,264 bytes  (excludes profiling overheads)

 COST CENTRE                       MODULE                          SRC
 %time %alloc

 MAIN                              MAIN                            <built-
 in>                                                      12.6    2.2

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13492>
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