Performances with gcj

Benjamin de Dardel benjamin.dedardel@gmail.com
Sun Aug 10 21:34:00 GMT 2008


Hi Francesco,

Thanks for your response. I had already tryed to optimize the code with 
the java file, but it didn't work :
$ gcj -0 --main=PipeTest -o test.bin PipeTest.java
gcj: unrecognized option '-0'

With class files, compilation works... but performances decrease !
May be it's beacause of the threads. I don't know. I'll do some other 
tests in the next days.

# test5
$ gcj -C PipeTest.java
$ gcj -O2 --main=PipeTest -o test.bin PipeTest.class Consumer.class 
Producer.class Filter.class

real    21m59.844s
user    5m26.070s
sys     9m52.130s

# test6
$ gcj -C PipeTest.java
$ gcj -O3 --main=PipeTest -o test.bin PipeTest.class Consumer.class 
Producer.class Filter.class

real    25m34.394s
user    6m12.250s
sys     11m4.440s

ffileppo a écrit :
>> 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
>
>
>
>
>   



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