Re: GCC/CFLAGS Benchmark for HEAD and PHP_5_0

I've done lots of testing with these kind of compiler flags. It's really a tough call because you might change 2 lines in the PHP code and then your results might differ completely because of CPU cache hits/misses. Also very much depends on the CPU. But in any case, interesting results. Andi At 08:30 PM 10/4/2004 +0200, Sebastian Bergmann wrote:

I ran the Zend/bench.php script with PHP 5.0 and PHP 5.1 compiled with GCC 3.3 and GCC 3.4 using different optimizations on my Intel Pentium-M laptop: HEAD (PHP 5.1.0-dev)

    GCC 3.3.4 (-march=pentium3)

      -O0:                          48.602
      -Os:                          29.920
      -O1:                          31.349
      -O2:                          29.029
      -O3:                          29.644

    GCC 3.4.2 (-march=pentium-m -mtune=pentium-m)

      -O0:                          48.966
      -Os:                          26.286
      -O1:                          29.253
      -O2:                          29.100
      -O3:                          27.767

      -fprofile-{generate|use} -Os: 24.216
      -fprofile-{generate|use} -O1: 26.575
      -fprofile-{generate|use} -O2: 26.339
      -fprofile-{generate|use} -O3: 25.537

PHP_5_0 (PHP 5.0.3-dev)

    GCC 3.3.4 (-march=pentium3)

      -O0:                          58.394
      -Os:                          42.570
      -O1:                          43.454
      -O2:                          42.092
      -O3:                          42.066

    GCC 3.4.2 (-march=pentium-m -mtune=pentium-m)

      -O0:                          59.272
      -Os:                          35.853
      -O1:                          38.275
      -O2:                          37.989
      -O3:                          41.020

      -fprofile-{generate|use} -Os: 33.926
      -fprofile-{generate|use} -O1: 36.853
      -fprofile-{generate|use} -O2: 35.335
      -fprofile-{generate|use} -O3: 38.897

For the -fprofile-{generate|use} builds I used the Zend/bench.php script, too, to generate the profile information. If we were to add Makefile target (like GCC itself ("make profiled-bootstrap")) to the PHP build that makes use of -fprofile-{generate|use} it would make sense to use "make test" to generate the profiling information. When I find the time I will repeat the benchmark on my AMD Athlon64 box because I think the small L1/L2 caches of the laptop CPU affect the performance of the bigger code generated through optimizations. You can clearly see that code optimized for size (-Os) is faster than the more aggressive -O1, -O2, and -O3 optimization levels. --

Sebastian Bergmann                      http://www.sebastian-bergmann.de/

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