Class.new is all you need

by Shia

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RubyKaigi 2026 LT Shia@STORES Class.new is all you need

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SIM SANGYONG (@shia) - STORES Inc. - GitHub: @riseshia - X: @riseshia Self Introduction 2

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SIM SANGYONG (@shia) - STORES Inc. - GitHub: @riseshia - X: @riseshia - And…Day 3!!! Self Introduction 3

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"type-guessr" needed to collect info from project code at startup and it was slow. So, I proﬁled and… Background 4

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ko1: "Class.new is faster than them" shia: "…!?!?" Background 5

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Target: Initialization speed - Data.deﬁne, Struct, Class - kwargs, positional args - 1 ivar, 8 ivars Ruby 4.0.1 / linux / no YJIT So, benchmark it 6

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Result 7 1 ﬁeld 8 ﬁelds

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- Class.new > Struct.new >> Data.deﬁne.new - kwargs are slow - more ivars, more slower Observation 8

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Observation 9 8 ﬁelds - Class.new > Struct.new >> Data.deﬁne.new - kwargs are slow - more ivars, more slower Note: Class.new outperforms with YJIT

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See perf results 10 "perf record -g --call-graph dwarf" Ruby 4.0.1 / linux / no YJIT / ivar 1 ﬁeld

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See perf results 11

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See perf results 12

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See perf results 13

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See perf results 14

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See perf results 15

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- Is kwargs initialization optimized? - Create Hash for kwargs on initialization or not - Is ivar access optimized? - Byte code caching with object shape applied or not - Does the object need to be frozen? Why?? 16

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shia: "I found it really is.." ko1: "We optimize what people use most, so yeah" shia: "That's absolutely true😂" After talk 17

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I originally used Data because I vaguely assumed Data/Struct was lighter than Class. Reality was diﬀerent at least object initialization. Did you know that? Summary 18

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〜Fin〜 19

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🤔 20

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If "Class" is the fastest, why not re-implement these with it?? 🤔🤔🤔 How to speed up Struct or Data.deﬁne 21

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Re-impl Struct with "Class", and benchmark again: (8 fields, YJIT off/on) How to speed up Struct or Data.define 22

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It’s really fast! Let’s submit this patch!!!

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Let’s submit this patch!!! 24

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Submit this patch…? 25

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🫠 26

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🚮 27

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28 You can check the full benchmark & RubyStruct implementation! https://github.com/riseshia/class-new-is-all-you-need Class.new might be all you need (if initialization perf matters)