When building Spark with build/mvn or dev/run-tests, a Java warning appears repeatedly on STDERR:
OpenJDK 64-Bit Server VM warning: ignoring option MaxPermSize=512M; support was removed in 8.0
This warning is due to build/mvn adding the -XX:MaxPermSize=512M option to MAVEN_OPTS. When compiling with Java 7, this parameter is essential. With Java 8, the parameter leads to the warning above.
Because build/mvn adds MaxPermSize to MAVEN_OPTS, even if that environment variable doesn't contain the option, setting MAVEN_OPTS to a string that does not contain MaxPermSize has no effect.