--- Steve Loughran <[EMAIL PROTECTED]> schrieb:
> Michael Meyer wrote:
> >> --- Steve Loughran <[EMAIL PROTECTED]> 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?
> >
> > In order to rule out any pathologies in my ant
> build
> > file or my source code, I benchmarked a compile
> run
> > again, this time the compilation of the Ant 1.7.0
> > source code.
> >
> > Additionally, I have deinstalled the powernowd
> > package, so the frequency of the cpu is not
> reduced
> > when idle, rather all the time at 2.4 GHZ (Intel
> Core
> > 2 Duo E6600).
> >
> > Compile run this time with:
> >
> > ant clean ; ant build ; ant clean ; sleep 10 ;
> time
> > ant build
> >
> > (This way, every file to be compiled and the jdk
> files
> > are preloaded into memory, and before the timed
> ant
> > build there is a wait period of 10 seconds so that
> the
> > journal daemon from the ext3 file system can write
> all
> > emitted byte code files (done every 5 seconds by
> > default) before the actual compile run starts.)
> >
>
> -this is interesting stuff. Stick it up on a web
> page and I'll point to it.
>
> At the same time, I dont know why it is happening.
> It does hint at
> something I've been seeing on my desktop though, in
> which builds in
> VMWare images (with a single CPU option) seem faster
> than the stuff on
> the main desktop.
>
> 1. I wonder if we are doing some kind of
> synchronisation on I/O that is
> causing us to take longer to acquire locks?
>
> 2. A good test would be to focus on javac and see if
> a .sh script to
> build the classes shows the same slowdown. if it
> does, its a javac
> problem. If it doesnt, its an ant problem.
I build a script which compiles every java class
except those in
apache-ant-1.7.0/src/main/org/apache/tools/ant/taskdefs/optional/ejb/
and the compile run took almost as long as the compile
run with 'ant build' on 1 core (both with 1 and 2
cores):
1 core:
-------
real 0m4.096s
user 0m3.884s
sys 0m0.168s
2 cores:
--------
real 0m3.694s
user 0m4.180s
sys 0m0.160s
the old complete compile run with ant (time ant
build) was:
1 core:
real 0m4.520s
user 0m4.312s
sys 0m0.176s
2 cores:
real 0m8.150s
user 0m14.849s
sys 0m0.400s
So each time is around 4 seconds, except the build
using ant with two cores.
After fiddling around with cpulimit on linux for some
time, I did not manage to reduce the ant build time on
two cores significantly.
But I guess solaris has more possibilities to limit
the processor usage or core usage of a single user. So
the build process might run as a different user and
this user could have limited cores available. This
should decrease the build time.
On mere build servers running linux one could disable
the second core at boot time permanently to reduce the
build time, if no other processes are running on this
server.
But on workstations the second core is often used by
the application being developed if it is
multithreaded, so there might be no way in linux to
reduce the build time wih two cores?
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