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Investigate deoptimization diagnostics tooling #44211
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Activity
May I request that be investigation public (Or already public but in somewhere)?
Very interested in this stuff.Reacted by intrnl, Erik, E-Liang Tan, Paul, Brian Kim, Dmitry Patsura, Max Lay, Hendry Sadrak, Yuya Tanaka, Radosław Miernik and 23 moreThere's already a tool for this: https://www.npmjs.com/package/deoptigate
Its very useful, shows all places where v8 switches to megamorphic IC.
Reacted by Erik and WJHReacted by Clifford Fajardo , Toni Villena, Erik, Chris Krycho, Degubi, Caleb Jasik, Kenta Moriuchi and Vitaly
We've been diving deep into perf. One place we find tooling lacking is in identifying deoptimizations in the VM. Ron Buckton (@rbuckton) has had some neat experiments which we might be able to leverage to identify polymorphic/megamorphic usage sites. Work closely with Andrew Casey (@amcasey) here to get a sense of what is and isn't useful.
Also, identify some baselines within the tooling to help drive meaningful goals for users. For example, a use-site might have 500 different object shapes passing through it - is it meaningfully faster to reduce that to 200?
Ideally, this would be usable by the broader team and partner teams who also write CPU-bound Node.js code.