The java launcher currently supports "-mx", "-ms" as equivalent to "-Xmx" and "-Xms". This support is there only for backward compatibility against very old Java versions. Usage of "-mx" and "-ms" (along with some other launcher options) will be deprecated for removal, shortly. There are some tests which currently use these options when launching the tests. Those should be updated to use "-Xmx" and "-Xms" instead.