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From Michael Meyer <mike65...@yahoo.de>
Subject Re: Ant build slower on two cores than on one core?
Date Sat, 08 Mar 2008 10:24:09 GMT
 --- Michael Meyer <mike65134@yahoo.de> schrieb: 
>  --- Steve Loughran <stevel@apache.org> schrieb: 
> > this is really interesting. I'd thought javac was
> > unthreaded too, but 
> > even so you'd expect file IO to work in the other
> > CPU, so get a boost 
> > from the second core.
> > 
> > what happens when you try a different javac, like
> > the eclipse one?
> 
> I have timed a very short compile run with different
> JDKs on the same machine, 
> using the same OS one time with both cores enabled,
> the other time with only 
> one core enabled. 
> 
> Result: the compile run using only one core was
> significantly faster than the
> one using both cores. This is true with every JDK I
> tried.
> 
> So this might be an ant specific phenomenom? Maybe
> ant
> is spawning threads?
.....

I did another test with a little bit more source code
to compile (3 KLOC) in order to make sure that the 
effect isn't solely the startup of the java vm.

Sun Java 6 Update 4:

1 core: 
real	0m2.346s
user	0m2.220s
sys	0m0.072s

2 cores:
real	0m4.013s
user	0m6.980s
sys	0m0.192s

A rather dramatic difference!?!?






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