Re:Performances with gcj

["ffileppo" <ffileppo@libero.it>]

> Hi all,
>
> I had to release a program that executes an external process and gets
> its standard output.
> I implemented a solution with threads and pipes to redirect inputs and 
> outputs (cf PipeTest.java).
>
> I choose the 'find /' command to test it.
> I'm very surprised about gcj performances which are 5x slowly than sun jvm.
> In fact, I expected that my compiled program would be faster than all jvm.
>
> Do you have an idea about these differences ?
> Is that the gnu classpath implementation which is quiet slow ?
>
> Regards,
> Benjamin
>
> # test1 : bash
> $ time find /
> real    2m6.054s
> user    0m5.260s
> sys     0m6.990s
>
> # test2 : compilation with gcj
> $ gcj --main=PipeTest -o test.bin PipeTest.java
> $ time test.bin
> real    18m50.632s
> user    4m56.380s
> sys     8m31.940s
>
> real    19m38.148s
> user    5m9.660s
> sys     9m44.710s
>
> # test3: interpretation with gij
> $ gcj -C PipeTest.java
> $ time gij PipeTest
>
> real    22m39.882s
> user    6m7.580s
> sys     10m26.350s
>
> # test4 : interpretation with java
> $ javac PipeTest.java
> $ time java PipeTest
> real    3m35.035s
> user    1m18.710s
> sys     0m11.730s
>
> ##### compilers #####
> $ gcj --version
> gcj (GCC) 4.2.3 (Ubuntu 4.2.3-2ubuntu6)
>
> $ javac -version
> javac 1.6.0_03
>

You need to pass -O2 or -O3 option to gcj compiler (no optimization is enabled by default).
Please take a look at other posts about gcj performance (http://gcc.gnu.org/ml/java/2008-05/msg00017.html).

Francesco