RFR: 8335347: GenShen: Revert change that has adaptive heuristic ignore abbreviated cycles

[Y. Srinivas Ramakrishna]

On Fri, 28 Jun 2024 16:22:03 GMT, William Kemper <wkemper at openjdk.org> wrote:

> Additional performance testing has shown no benefit from this feature. In fact, latency is degraded on the extremem benchmark with this feature enabled.

Did we compare degenerated cycle count for more spiky or variable load benchmarks, where the original fix was supposed to help.

I also wonder if instead of the "bang, bang" control (completely ignore abbreviated as was the previous fix, now withdrawn vs treat abbreviated numbers on par with non-abbreviated cycles), I wonder if you might maintain two decaying averages for the two types separately, then toss a coin whose probability is based on the decaying ratio of the two types of events, and use the decaying average value of the corresponding type or the other based on the result of the coin toss. In effect, you are simulating and trying to predict the probability of a long or short cycle, and using the appropriate measure. Not sure how that would behave since the value seems to be continuously calculated, it would probably effectively revert to the same value as the decaying average gives without doing this more complex simulation.  :-)

Anyway, was just thinking out loud here...

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PR Comment: https://git.openjdk.org/shenandoah/pull/455#issuecomment-2197470115