RFR: Allow young collection to suspend marking in old generation [v14]

[earthling-amzn]

On Mon, 1 Mar 2021 14:10:37 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> earthling-amzn has updated the pull request incrementally with three additional commits since the last revision:
>> 
>>  - Encode active generation and old generation marking status
>>  - Do not unset preemption request flag prematurely
>>  - Disable reference processing generational mode
>
> src/hotspot/share/gc/shenandoah/shenandoahOldGeneration.cpp line 1:
> 
>> 1: #include "precompiled.hpp"
> 
> Missing header.

Wow, I sure did miss a lot of copyright headers. Can `git jcheck` be made to check for this?

> src/hotspot/share/gc/shenandoah/shenandoahPhaseTimings.hpp line 103:
> 
>> 101:                                                                                        \
>> 102:   f(init_update_refs_gross,                         "Pause Init Update Refs (G)")      \
>> 103:   f(init_update_refs,                               "Pause Init Update Refs (N)")      \
> 
> Looks like unrelated spacing changes

Do you want me to revert this and put it in a separate PR? Maybe when we add a phase for remembered set scanning?

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PR: https://git.openjdk.java.net/shenandoah/pull/19