Try this on your multimodule maven build and watch the performance difference !

gistfile1.txt

           <plugin>
               <groupId>org.apache.maven.plugins</groupId>
               <artifactId>maven-compiler-plugin</artifactId>
               .....
               <dependencies>
                   <dependency>
                       <groupId>org.codehaus.plexus</groupId>
                       <artifactId>plexus-compiler-javac</artifactId>
                       <version>1.8.6</version>
                   </dependency>
               </dependencies>
           </plugin>

Btw; it's http://jira.codehaus.org/browse/PLXCOMP-202

Seems to have dropped our 15 minute, Maven 3 (w/ multithreads) build to under 10! Thanks!