@Override
    protected void setup(Context context) throws IOException, InterruptedException {
      this.cmd = forName(context.getConfiguration().get(CMD_KEY), Test.class);

      // this is required so that extensions of PE are instantiated within the
      // map reduce task...
      Class<? extends PerformanceEvaluation> peClass =
        forName(context.getConfiguration().get(PE_KEY), PerformanceEvaluation.class);
      try {
        peClass.getConstructor(Configuration.class).newInstance(context.getConfiguration());
      } catch (Exception e) {
        throw new IllegalStateException("Could not instantiate PE instance", e);
      }
    }
configuration parameter name that contains the PE impl
hbase-diagnostics/src/main/java/org/apache/hadoop/hbase/PerformanceEvaluation.java