RFR: JDK-8276422 Add command-line option to disable finalization [v3]

[David Holmes]

On Fri, 19 Nov 2021 02:29:33 GMT, Stuart Marks <smarks at openjdk.org> wrote:

>>> When the finalization is disabled, perhaps jcmd GC.finalizer_info should just be made as a nop in the VM.
>> 
>> Yes that is a trivial change to add. @stuart-marks I can provide the code. You can choose whether to include in this PR or else we can do a follow-up.
>
>> > When the finalization is disabled, perhaps jcmd GC.finalizer_info should just be made as a nop in the VM.
>> 
>> Yes that is a trivial change to add. @stuart-marks I can provide the code. You can choose whether to include in this PR or else we can do a follow-up.
> 
> Seems simple enough. Is there any testing that needs to be done for this? Does jcmd output require CSR review? I guess there would be a compatibility issue if there were something that was parsing the output of jcmd. Or is it solely intended to be read by humans?

@stuart-marks No CSR needed for this as no output format is specified. Plus this command already has a simple text response when there are no finalizers queued. E.g.
``` 
> ../build/linux-x64-debug-finalization/images/jdk/bin/jcmd 27939 GC.finalizer_info
27939:
No instances waiting for finalization found

so when finalization is disabled this just becomes:
``` 
> ../build/linux-x64-debug-finalization/images/jdk/bin/jcmd 28018 GC.finalizer_info
28018:
Finalization is disabled

There is a test for this Dcmd, but it doesn't test the "nothing here" case so I don't think it is necessary to augment it for this case:
`hotspot/jtreg/serviceability/dcmd/gc/FinalizerInfoTest.java`

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PR: https://git.openjdk.java.net/jdk/pull/6442