RFR: 8319650: Improve heap dump performance with class metadata caching [v3]

[Aleksey Shipilev]

On Thu, 9 Nov 2023 15:18:59 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Yeah. What is the proper idiom for "I do not want this to be allocated (in C heap or anywhere else) without NMT knowing"? `StackObj` is the closest I can get nowadays, I think. `ValueObj` is gone since JDK 11: https://bugs.openjdk.org/browse/JDK-8199282
>
> yes, everything without a base class is a ValueObj and there's a link-time error if you try to call 'new' on it. The ValueObj base class was problematic.  Now it's just omitted.

Got it. Dropped `StackObj`. Indeed, if I try to do `new ...Table()`, I get a link-time error.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16545#discussion_r1388175438