[jdk21u-dev] RFR: 8322279: Generational ZGC: Use ZFragmentationLimit and ZYoungCompactionLimit as percentage instead of multiples

[Liang Mao]

On Tue, 16 Jan 2024 09:17:32 GMT, Goetz Lindenmaier <goetz at openjdk.org> wrote:

> Hi @mmyxym, please give a risk estimate. What will be the effects of this this change? It looks as if a heurisitc will be changed by a factor of 100. Will normal ZGC be affected? Any other GC? Will pause time, heap size etc be affected?

Hi, I think the risk is quite low because the genz author @fisk treated it as a trivial fix and the actual behaviors changed by the commit is not critical that it only affects the decision of per cpu shared small page and aging heuristics. The change will make the policy decision more reasonable. The commit doesn't affect the behavior of normal ZGC or other GCS and won't affect those major metrics like pause time or heap size, etc.

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PR Comment: https://git.openjdk.org/jdk21u-dev/pull/173#issuecomment-1893480962