RFR: 8254739: G1: Optimize evacuation failure for regions with few failed objects [v19]

[Hamlin Li]

On Fri, 5 Nov 2021 11:18:31 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> @Hamlin-Li : I think @albertnetymk concern is that typically an `iterate` method does not modify the list itself. That is surprising for readers. The documentation also does not indicate any of that. I do not think he believes this will cause a VM failure.
>> 
>> Maybe change `HeapRegion::iterate_evac_failure_objs` to call a (new) `drop()` method on `_evac_failure_objs`?
>> 
>> I think such a change would solve Albert's concerns.
>> 
>> An alternative could be renaming `iterate` to something else.
>
> Thank Thomas for unpacking my concern more precisely. I used "problematic" to mean the second iteration will not do what developers expect it to do, not necessarily a VM crash.

Thanks for your clarification, Albert, Thomas, I see your point, it make sense to me.

As this patch has been blocking some other issues for a while, and I think it's better to think of some good solution for Albert's concern (seems add a drop is a little bit redundant for me :).) 

If you don't mind, can I do this refinement later in another issue? Thanks

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PR: https://git.openjdk.java.net/jdk/pull/5181