RFR: 8332455: Improve G1/ParallelGC tasks to not override array lengths

[Kim Barrett]

On Fri, 5 Jul 2024 15:04:01 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> One idea that I just now had (for my particular problem in Lilliput2) is this: we only need the length-field in the from-space copy to keep the actual length of the array, so that we know when to stop, and also to restore the length in the to-space copy. We could copy the length to the from-space offset 8 (instead of 4, which is the length field with Lilliput2), and use that, instead. That should be ok, because surely we don't need to do the slicing for 0-length arrays (in which case we would stomp over the next object), and for larger arrays, we don't care about the from-space elements just like we don't care about the length.

That still doesn't permit parallelizing the processing in the evac-failure case.

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PR Comment: https://git.openjdk.org/jdk/pull/19282#issuecomment-2217239553