RFR: 8255231: Avoid upcalls when initializing the statSampler [v2]

[Claes Redestad]

On Sat, 24 Oct 2020 05:13:44 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Revert unrelated changes to perfData
>
> src/hotspot/share/runtime/statSampler.cpp line 217:
> 
>> 215:  */
>> 216: 
>> 217: // stable interface, supported counters in the JAVA_PROPERTY name space
> 
> * The list of System Properties that have corresponding PerfData
>  * string instrumentation created by retrieving the named property's
>  * value from System.getProperty() and unconditionally creating a
>  * PerfStringConstant object initialized to the retrieved value. This
>  * is not an exhaustive list of Java properties with corresponding string
>  * instrumentation as the create_system_property_instrumentation() method
>  * creates other property based instrumentation conditionally.
> I found the above comment unreadable. Is it possible to clarify it?

I reworked it a bit to get rid of the static array and keep comments more coherent. I think it reads a bit better now.

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PR: https://git.openjdk.java.net/jdk/pull/802