private <Type> Class<? extends Type> forName(String className, Class<Type> type) {
      try {
        return Class.forName(className).asSubclass(type);
      } catch (ClassNotFoundException e) {
        throw new IllegalStateException("Could not find class for name: " + className, e);
      }
    }
configuration parameter name that contains the PE impl
hbase-diagnostics/src/main/java/org/apache/hadoop/hbase/PerformanceEvaluation.java