RFR: 8330847: G1 accesses uninitialized memory when predicting eden copy time

[Thomas Schatzl]

On Thu, 23 May 2024 11:03:41 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review this change that fixes survivor rate predictor initialization when expanding the survivor rate prediction tables.
> 
> Before JDK-8231579 these predictors were not used when finalizing the collection set at gc start, and were always updated properly at the end of the GC. With that change G1 started using these uninitialized predictors.
> 
> There is an assert that should fail in the future if there is a bug.
> 
> Testing: tier1-3
> 
> Thanks,
>   Thomas

Fwiw, `G1SurvRateGroup::accum_surv_rate_pred` adds some assert/self verification code that actually already fails building the VM without this change.

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PR Comment: https://git.openjdk.org/jdk/pull/19364#issuecomment-2128761889