Bogus stats when running SMP programs

[Tomasz Zielonka]

On Tue, Sep 26, 2006 at 01:46:30AM +0100, Ian Lynagh wrote:
> I couldn't reproduce this with a simple program that forked off 4
> threads to do computation on a single CPU machine, and neither could
> someone on IRC with head from Sep 15 on a Core Duo.
> 
> Is it possible to send us a small example program along with exactly
> what flags you used to compile and run it please?

It turns out it happens even with the simplest program:

    main = return

Compilation command:

    ghc -threaded --make B -o B

Running:

    tomekz at gfs6:~/src/par$ ./B +RTS -sstderr
    ./B +RTS -sstderr
         21,864 bytes allocated in the heap
          1,404 bytes copied during GC (scavenged)
          4,156 bytes copied during GC (not scavenged)
         21,936 bytes maximum residency (1 sample(s))

              1 collections in generation 0 (  0.00s)
              1 collections in generation 1 (  0.00s)

              1 Mb total memory in use

      Task  0 (worker) :  MUT time: 402094045.13s  (  0.00s elapsed)
                          GC  time:   0.00s  (  0.00s elapsed)

      Task  1 (worker) :  MUT time: 200.00s  (  0.00s elapsed)
                          GC  time:   0.00s  (  0.00s elapsed)

      Task  2 (worker) :  MUT time:   0.00s  (  0.00s elapsed)
                          GC  time:   0.00s  (  0.00s elapsed)

      INIT  time    0.00s  (  0.00s elapsed)
      MUT   time    0.00s  (  0.00s elapsed)
      GC    time    0.00s  (  0.00s elapsed)
      EXIT  time    0.00s  (  0.00s elapsed)
      Total time    0.00s  (  0.00s elapsed)

      %GC time       0.0%  (11.5% elapsed)

      Alloc rate    21,864,000,000 bytes per MUT second

      Productivity 100.0% of total user, 0.2% of total elapsed

It doesn't happen when I compile without -threaded. But it doesn't show
task statistics then.

Can it have something to do with using gcc-4.1.2?

Perhaps I should try compiling GHC on my machine. Right now I am using
a precompiled snapshot.

Best regards
Tomasz