We occasionally get javac errors:

  [javac] Error occurred during initialization of VM
  [javac] Could not reserve enough space for object heap
  [javac] Error: Could not create the Java Virtual Machine.
  [javac] Error: A fatal exception has occurred. Program will exit.

We are using maxmemory=128m:

    <target name="run" depends="init,compile,-pre-jar,jar">
        <java jar="${dist.jar}"
           fork="true"
           failonerror="true"
           maxmemory="128m"/>
    </target>

Machine has 128GB of RAM.

We see this in like 5% of our builds (nightly and/or continuous integration
infrastructure). Rerunning the build succeeds.

How can we go about tracking down the issue? Are the extra flags we can add?