RFR: 8342444: Shenandoah: Uncommit regions from a separate, STS aware thread [v3]

[William Kemper]

On Tue, 19 Nov 2024 02:03:18 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Prevent uncommit thread from running during GC
>
> Looks good to me. A few documentation comment requests.
> 
> Also please share performance data in this PR or in the ticket, especially from the perf/benchmark that may have precipitated this change.

@ysramakrishna - I ran several iterations of specjbb2015 with different variations of polling interval. Results show that 1/10th of `ShenandoahUncommitDelay` is reasonable, and avoids unintentional commit delays when the polling interval is equal or greater than `ShenandoahUncommitDelay`.


                      Category |  Count |         Total |      GeoMean |      Average |     Trim 0.1 |       StdDev |      Minimum |      Maximum
openjdk:master   critical_jops |      5 |     50862.000 |    10162.095 |    10172.400 |    10172.400 |      513.605 |     9630.000 |    10882.000                                
30ms polling     critical_jops |      5 |     48035.000 |     9582.113 |     9607.000 |     9607.000 |      778.036 |     8808.000 |    10692.000
30s polling      critical_jops |      5 |     56398.000 |    11272.026 |    11279.600 |    11279.600 |      460.355 |    10627.000 |    11842.000
no polling       critical_jops |      5 |     55917.000 |    11176.046 |    11183.400 |    11183.400 |      460.960 |    10899.000 |    11995.000

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PR Comment: https://git.openjdk.org/jdk/pull/22019#issuecomment-2501826875