Hints for setting mem options of maven&plug-ins (for parallel builds)
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Key: MNG-5100
URL: http://jira.codehaus.org/browse/MNG-5100
Project: Maven 2 & 3
Issue Type: Improvement
Components: Documentation: Guides
Affects Versions: 3.0.3
Reporter: Kari J. Niemi
(I enabled parallel builds of maven3 for my project in CI server, it was
running quite nicely giving me much faster builds for a multi-module build.
But... it brought our CI server on it's knees, other projects suffered from
this and the CI build server admin bashed me to get back to serial build :D...
oh, he's such a nice guy :D...)
I did some googling around and found out that in Linux, forking new processes
may be extremely slow in case the parent that forks, has a great memory print.
Well, in the past I had (of course) optimized my build for maven2 by throwing
it more (some? no,no... _lots_ of) memory with MAVEN_OPTS by setting both Xms
and Xms to the same huge value, not forgetting the MaxPermSize and PermSize. I
suppose this, together with the linux forking "feature", might cause the
extreme cpu load? And of course the CI server process itself has an even bigger
memory print, times ten or something, fortunately I suppose it's not doing so
much forking...
I suppose the memory tuning should/could be done quite differently when using
parallel build feature because the mem is then used in the forked processes
which are smaller? So in parallel build I might set those mem options pretty
low, I guess? And also I could be setting "-client"-mode manually -because
otherwise jvm would think it should be running in server mode (due to running
in server HW. Actually I don't quite understand why jvm anyway decides based on
HW whether it should be running in server or client mode - there's no such
relation -not every jvm running on server HW is really a server process...)
Is there anything that we could be improve in maven/maven documentation in this
respect?
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