RFR: 8368465: [leyden] Improve precompiler method selection code [v4]

[Vladimir Kozlov]

On Fri, 17 Oct 2025 21:35:04 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Forked from [JDK-8366681](https://bugs.openjdk.org/browse/JDK-8366681): there are still some cleanups/performance improvements possible. Current selection code is a bit hairy, and turns out the changes I made for previous patch improve performance.
>> 
>> Notable improvements:
>>  1. Push the compilation level filters downwards. This allows compiling A2 from T2/T3 code more easily, and allows to implement policies for compiling on any A* level based on observing top-compiled T* levels.
>>  2. Sort methods by hotness and code size. This looks to have a positive effect on shorter workloads, I suspect because we are avoiding a lot of C1 compilations by preloading hottest code first.
>> 
>> Additional testing:
>>  - [x] Performance tests (see comments)
>>  - [x] Linux x86_64 server fastdebug, `runtime/cds`
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Drop the mention of MDO

An other suggestion for this concurrent preloading would be to split A4 preload code. One set is the current which needs to wait `compute_java_loaders()`. And new one (much smaller) is for simple methods for classes which are loaded first (String, for example) which we can preload much sooner.

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PR Comment: https://git.openjdk.org/leyden/pull/99#issuecomment-3417553909