@Override
  protected final void postSetUp() throws Exception {
    diskProps.setDiskDirs(dirs);
    log = ds.getLogWriter();
  }
To run DiskRegionRollOpLogPerfJUnitTest to produce the Perf numbers set runPerfTest to true.
Also ,one needs to set the VM heap size accordingly. (For example:Default setting in build.xml
is <jvmarg value="-Xmx256M"/>
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/diskPerf/DiskRegionRollOpLogJUnitPerformanceTest.java