RFR: 8296344: Remove dependency on G1 for writing the CDS archive heap [v5]

[Thomas Schatzl]

On Tue, 14 Feb 2023 05:48:26 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> Goals
>> 
>> - Simplify the writing of the CDS archive heap
>>     - We no longer need to allocate special "archive regions" during CDS dump time. See all the removed G1 code. 
>> - Make it possible to (in a future RFE) write the CDS archive heap using any garbage collector
>> 
>> Implementation - the following runs inside a safepoint so heap objects aren't moving
>> 
>> - Find all the objects that should be archived
>> - Allocate buffer using a GrowableArray
>>     - Copy all "open" objects into the buffer
>>     - Copy all "closed" objects into the buffer
>> - Make sure the heap image can be mapped with all possible G1 region sizes: 
>>     - While copying, add fillers to make sure no object spans across 1MB boundary (minimal G1 region size)
>>     - Align the bottom of the "open" and "closed" objects at 1MB boundary
>> - Write the buffer to disk as the image for the archive heap
>> 
>> Testing: tiers 1 ~ 5
>
> Ioi Lam has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:
> 
>  - Merge branch 'master' into 8296344-remove-cds-heap-dump-dependency-on-G1-public-review
>  - @calvinccheung review comment -- added assert)
>  - Simplified relocation by using buffered address instead of requested address
>  - @ashu-mehra review; added comments about relocating HeapShared::roots()
>  - fixed windows and 32-bit builds which do not support archive heap
>  - clean up
>  - 8296344: Remove dependency on G1 for writing the CDS archive heap (step 2: no intermediate buffer)
>  - 8296344: Remove dependency on G1 for writing the CDS archive heap (step 1: with buffer copying)

GC parts look good

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Marked as reviewed by tschatzl (Reviewer).

PR: https://git.openjdk.org/jdk/pull/12304