[jdk21u-dev] RFR: 8331572: Allow using OopMapCache outside of STW GC phases [v3]

[Paul Hohensee]

On Thu, 8 Aug 2024 16:31:09 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Unclean backport to improve GC and general stack walk performance when walking interpreted frames.
>> 
>> This is one of few backports that gets `OopMapCache` behavior similar to mainline. This makes [JDK-8335409](https://bugs.openjdk.org/browse/JDK-8335409) backport easier, because it avoids lots of conflicts, resolving which might introduce surprising bugs. Aligning this code with mainline makes accidents less likely.
>> 
>> The point of uncleanliness comes from the way we hook up the cleanup notifications to Service Thread. In later JDKs, [JDK-8329488](https://bugs.openjdk.org/browse/JDK-8329488) made Service Thread wake up regularly to do various cleanups. In JDK 21, we still need to hook up the clean up to the "usual" place in safepoint epilog.
>> 
>> Additional testing:
>>  - [x] Linux x86_64 server fastdebug, `all`
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8331572-oopmap-cache-all
>  - Backport 05ff3185edd25b381a97f6879f496e97b62dddc2
>  - Merge branch 'master' into JDK-8331572-oopmap-cache-all
>  - Backport d999b81e7110751be402012e1ed41b3256f5895e

Marked as reviewed by phh (Reviewer).

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PR Review: https://git.openjdk.org/jdk21u-dev/pull/610#pullrequestreview-2233154798