RFR: 8349814: [leyden] Reduce uncommon traps in preload code [v3]

[Vladimir Ivanov]

On Fri, 21 Feb 2025 12:56:44 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Preload code is the C2 code we load very early, before it gets substituted by more advanced C2 code. We are seeing lots of uncommon traps from the preloaded code, though, which invalidates it too early. We can do precompile code without uncommon traps to alleviate this. 
>> 
>> Additional testing:
>>  - [x] Ad-hoc perf tests (see comment below)
>>  - [x] Linux x86_64 server fastdebug, `runtime/cds`
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Shuffle things around to capture more cases
>  - Comment
>  - Fix

Looks good.

src/hotspot/share/runtime/deoptimization.cpp line 2134:

> 2132:         // Compiler logs all uncommon traps with -Xlog:scc. That log is noisy, and some traps may be
> 2133:         // legitimate. Here, we log the problems that really caused the deopts at runtime.
> 2134:         log_warning(deoptimization)("In preload code: reason=%s action=%s method=%s",

Does it warrant a warning though? It can become quite noisy and users don't have any way to address the problem. `log_info`    looks a better fit here (and, probably, narrow the category to `scc+deoptimization`).

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Marked as reviewed by vlivanov (Committer).

PR Review: https://git.openjdk.org/leyden/pull/38#pullrequestreview-2636223983
PR Review Comment: https://git.openjdk.org/leyden/pull/38#discussion_r1967168143