jenkins slaves out of memory

[Ohad Basan]

Hello

I see jobs failing on out of memory problem
[ERROR] OutOfMemoryError: Increase heap size or lower gwt.jjs.maxThreads
http://jenkins.ovirt.org/job/ovirt-engine_create_rpms/label=f19-gwt/1211/console
can anyone plz recommend to me what should be changed and for what value? 
current mavenopts are
export MAVEN_OPTS="-XX:MaxPermSize=768m -Xmx512m -Djava.io.tmpdir=$WORKSPACE/tmp"

Thanks,

Ohad