I used -XX:+PerfDataSaveToFile to generate a hsperf data file and then I used jstat to print the "sun.os.hrt.frequency", but it display nothing. I have to use "-snap" option and grep that variable.

Steps to reproduce:
1. Go to any JDK demo, run java -XX:+PerfDataSaveToFile, you will see a hsperfdata_xxxx file generated when the app exits.
2. Run jstat on that file,
jstat -J-Djstat.showUnsupported=true -name "sun.os.hrt.frequency" file:///<path to hsperfdata file>
3. It prints nothing.