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All the Perl that's Practical to Extract and Report

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  • Just out of curiosity, it would be nice to know whether the traditional wisdom of overcommitting by one processor works (that is, is -j3 really faster than -j2), and also how much overovercommitting (-j4) trashes the systems?
    • by pudge (1) on 2003.09.19 11:07 (#24344) Homepage Journal
      I was kinda wondering the same thing myself ... but it takes so long to do each build, I don't want to spend the time doing the benchmarks! :-)

      make -j2, G5:
      real    2m11.921s
      user    3m26.660s
      sys     0m45.240s
      make -j3, G5:
      real    2m13.723s
      user    3m29.480s
      sys     0m49.440s
      make -j4, G5:
      real    2m25.240s
      user    3m31.290s
      sys     0m50.420s
      make -j10, G5:
      real    2m24.177s
      user    3m30.840s
      sys     0m50.500s
      So it actually looks like -j2 is slightly faster. I did both -j2 and -j3 twice, with similar results: -j2 is faster by a good second or two. And I also did -j4 more times, with similar results (slower than -j2 and -j3 by at least several seconds).

      One interesting note: Encode is always the last to finish. I wonder if making Encode begin to compile first would speed up the results somewhat. So with this run, I moved lib/auto/Encode/Encode.bundle to the beginning of dynamic_ext in the Makefile after Configure -des, and before make.

      make -j2, G5, putting Encode first:
      real    2m12.722s
      user    3m26.750s
      sys     0m47.140s
      make -j3, G5, putting Encode first:
      real    2m13.575s
      user    3m30.260s
      sys     0m48.490s
      Hm. Never mind. In the last test there, Encode STILL finished last, BTW.