RFR: 8332082: Shenandoah: Use consistent tests to determine when pre-write barrier is active [v3]

[William Kemper]

On Mon, 20 May 2024 16:59:25 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> This is consistent with c1 and other platforms.
>
> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix typo

Total time here is defined as the sum of 10 measurement runs for each of the 20 working benchmarks in the dacapo suite. The total time was taken for `jdk:master` and this PR with `-XX:TieredStopAtLevel=1` to keep all benchmarks running in C1.

jdk:master:
  Category |  Count |         Total |      GeoMean |      Average |     Trim 0.1 |       StdDev |      Minimum |      Maximum
    result |    200 |   2110857.000 |     7656.397 |    10554.285 |     9063.875 |     8894.464 |     1159.000 |    36836.000

This PR:
  Category |  Count |         Total |      GeoMean |      Average |     Trim 0.1 |       StdDev |      Minimum |      Maximum
    result |    200 |   2139852.000 |     7711.781 |    10699.260 |     9129.150 |     9166.330 |     1167.000 |    37336.000

This is a 1.4% increase in total time when running with just C1. The increase at trimmed mean 10% is just 0.7%. I'm okay with this.

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PR Comment: https://git.openjdk.org/jdk/pull/19180#issuecomment-2127724163