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Re: Ant build slower on two cores than on one core?

Steve Loughran

2008-03-07

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Michael Meyer wrote:
> Hi,
>
> I have a project that uses javac and a bit latex2html.
> Ant version is 1.7.0. The javac is from the original
> Sun JDK 6 Upodate 4. The OS is Ubuntu Linux.
>
> When ant invokes the javac compiler the compilation
> lasts longer on two cores than on one core (maxcpus=1
> at the grub prompt).
>
> This is strange:
> I thought javac is not threaded? But top shows a java
> process with up to 200% cpu usage on my dual core
> machine.
>
> I tried to limit it with cpulimit -e java -l 100, but
> the cpu usage still rises above 100%.
>
> Does anybody know how I could get the faster compile
> times that I get with only one core activated - but
> without deactivating the second core?


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?


--
Steve Loughran            http://www.1060.org/blogxter/publish/5
Author: Ant in Action       http://antbook.org/

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