RFR: 8337505: Footprint and startup regressions up to 20% in GUI apps

[Phil Race]

On Mon, 28 Oct 2024 21:26:38 GMT, Phil Race <prr at openjdk.org> wrote:

> https://bugs.openjdk.org/browse/JDK-8338677 already improved things for this so that's good.
> 
> This fix adds to it lazy initialisation of VarHandles in StrikeCache at the cost of some extra code.
> Since these VarHandles get used more or less immediately on Linux this new fix won't further improve matters there
> But should help on Mac where they aren't usually needed at startup
> And Windows is somewhere in between.

> I suspect dropping `static final` from these `VarHandle`-s would degrade performance, as some internal checks in `VHs` would not constant-fold.
> 
> Do you need these in isolation, or can you lazily-initialize them all at once? You can use "holder class" pattern like:
> 
> ```
>   static class VHHolder {
>     static final VarHandle xAdvanceHandle = ...
>   }
> ```



> I suspect dropping `static final` from these `VarHandle`-s would degrade performance, as some internal checks in `VHs` would not constant-fold.
> 
> Do you need these in isolation, or can you lazily-initialize them all at once? You can use "holder class" pattern like:
> 
> ```
>   static class VHHolder {
>     static final VarHandle xAdvanceHandle = ...
>   }
> ```

I've been told about this static final optimisation but I've never observed any measurable benefit in other code where I've tried hard to see it.
Performance (runtime) isn't a huge concern for this code. Won't be noticed
Start up is noticed. And on Windows *some* are used early but not all which is why I chose this approach

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PR Comment: https://git.openjdk.org/jdk/pull/21748#issuecomment-2445434568