RFR: 8331087: Move immutable nmethod data from CodeCache [v2]

Mon Apr 29 14:54:06 UTC 2024

On Mon, 29 Apr 2024 06:33:09 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

> Looks good to me. Did you measure any impact on performance (potentially due to improved code density)?

Thank you, @TobiHartmann, for review.

> What's left for [JDK-7072317](https://bugs.openjdk.org/browse/JDK-7072317)?

Make Relocation info (10% of nmethod size) immutable by moving all encoded pointers (external words and others, which we need to patch in Leyden when loading cached code) from it into separate mutable section.

> I wonder if the `CHECKED_CAST` changes shouldn't go into a separate RFE.

No, I want clear information which cast failed instead of trying to reproduce very intermittent failure like this: [JDK-8331253](https://bugs.openjdk.org/browse/JDK-8331253). When you have several `checked_cast<T>` in one method it is impossible to find which failed without this macro.

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PR Comment: https://git.openjdk.org/jdk/pull/18984#issuecomment-2082953366