RFR(S): 8168305 GC.class_stats should not require -XX:+UnlockDiagnosticVMOptions

[Marcus Larsson]

Hi Staffan,


On 2016-10-27 10:36, Staffan Larsen wrote:
> All,
>
> Please review this small patch to remove the requirement -XX:+UnlockDiagnosticVMOptions when running the GC.class_stats diagnostic command. Diagnostic commands are used for diagnosing problems and should not require restarting the JVM with a different command line flag if this can be avoided.
>
> While fixing this I also noticed that VM.print_touched_methods said it required -XX:+UnlockDiagnosticVMOptions, while what it really required was -XX:+LogTouchedMethods (which in turn requires -XX:+UnlockDiagnosticVMOptions) so I changed the error message here. In this case I think it is ok to require a special command line flag since collecting the information comes with an overhead.
>
> I have verified the fix manually and by running these tests: hotspot/test/runtime/CommandLine/PrintTouchedMethods.java hotspot/test/serviceability/sa/TestInstanceKlassSize.java hotspot/test/serviceability/sa/TestInstanceKlassSizeForInterface.java
>
> bug: https://bugs.openjdk.java.net/browse/JDK-8168305
> webrev: http://cr.openjdk.java.net/~sla/8168305/webrev.01/

The command description still mentions the flag, see
src/share/vm/services/diagnosticCommand.hpp:389

Apart from that this looks good to me!

Thanks,
Marcus

>
> Thanks,
> /Staffan