RFR: 8272147: Consolidate preserved marks handling with other STW collectors

[Thomas Schatzl]

On Mon, 5 Jun 2023 17:00:14 GMT, Guoxiong Li <gli at openjdk.org> wrote:

>> src/hotspot/share/gc/shared/preservedMarks.hpp line 60:
>> 
>>> 58: 
>>> 59: public:
>>> 60:   OopAndMarkWordStack& get_stack() { return _stack; }
>> 
>> Could you explain why this new API is required for Serial but not other collectors, e.g. G1? (IOW, can Serial do sth similar as G1 so that no new API is introduced?)
>
> The methods `MarkSweep::adjust_pointer` and `PreservedMarks::adjust_during_full_gc` have different implementations. The method `MarkSweep::adjust_pointer` seems doing more thing. So in `MarkSweep::adjust_marks`, I use `get_stack` to get the stack and invoke `MarkSweep::adjust_pointer` explicitly. If you can confirm `PreservedMarks::adjust_during_full_gc` is good to replace `MarkSweep::adjust_pointer`, I will remove `get_stack` and use `PreservedMarks::adjust_during_full_gc` instead of `MarkSweep::adjust_pointer`.

You can replace that code with `PreservedMarks::adjust_during_full_gc` from what I can see; the additional code in `MarkSweep::adjust_pointer` only deals with the generic case if the passed `oop` is null, which can't be the case for oops in the preserved marks set.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14274#discussion_r1219129319