RFR: 8316180: Thread-local backoff for secondary_super_cache updates [v5]

[Vladimir Ivanov]

On Wed, 27 Sep 2023 17:33:43 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Well, maybe :) One might ask another question: if I am experimenting with the value of this option, by switching from non-zero default to another non-zero value for performance evaluation in the field, is it really "diagnostic"? I think "experimental" captures the whole thing better. But I can change to diagnostic, if you insist.
>
> A better question to ask is "Why do I have to specify -XX:+UnlockExperimentalVMOptions to turn the feature OFF?". Diagnosing a performance anomaly may involve both turning the logic off or increasing the limit. So, I do think that diagnostic is a better fit here.

Another question: should the flag be platform-specific? I'd expect different platforms may eventually settle on different defaults (e.g., platforms w/o support should set it to 0 right away) and, also, it would be better to print warnings when users try to explicitly   set the flag to non-zero value when proper support is missing.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15718#discussion_r1338971022