RFR: 8305898: Alternative self-forwarding mechanism [v4]

[Roman Kennke]

On Fri, 9 Feb 2024 10:40:24 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

> This adds a branch to oopDesc::forwardee. Do you have an GC time measurements to show that this isn't causing a regression?

I just ran the (young-GC-heavy) derby benchmark, with more iterations, which does about 1600 GC cycles. Those are the average GC times of young GCs, running with G1:
baseline: 2.88624ms
selffwd: 2.88000ms

With Parallel GC, I get:
baseline: 2.80709
selffwd:  2.74724

When repeating the experiment I get similar results, sometimes baseline is slightliy better, sometimes selffwd is slightly better, but I don't see anything that would support a 'regression' with selffwd.

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PR Comment: https://git.openjdk.org/jdk/pull/17755#issuecomment-1935906844