RFR: 8323079: Regression of -5% to -11% with SPECjvm2008-MonteCarlo after JDK-8319451

Tue Jun 11 11:11:22 UTC 2024

Hi,

I cannot explain the regression, comparing the current mainline to JDK-21 reveals a decrease in performance, yet it is only for some combinations of OS-GC and perfasm shows that the hot regions (>99% of execution time) do not contain differences that can explain the results.

Consequently, with the advice of @TobiHartmann , I propose to effectively revert JDK-8319451 for the generation of `CMove`s inside loops. For those outside, the before-JDK-8319451 probability threshold is 0.001 and the current value is 0.01. I think the current value is more reasonable as evidenced by the benchmark added in JDK-8319451.

Please kindly review, thank you very much.
Quan Anh

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Commit messages:
 - JDK-8323079

Changes: https://git.openjdk.org/jdk/pull/19650/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19650&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323079
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/19650.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19650/head:pull/19650

PR: https://git.openjdk.org/jdk/pull/19650