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

[Staffan Larsen]

Thanks Ioi!

> On 27 Oct 2016, at 19:21, Ioi Lam <ioi.lam at oracle.com> wrote:
> 
> Looks good.
> 
> Thanks
> - Ioi
> 
> On 10/27/16 2:41 AM, Marcus Larsson wrote:
>> 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
>> 
>