Introducing the JetStream 3 Benchmark Suite

WebKit introduces JetStream 3.0, a major benchmark suite update that fundamentally changes how browser performance is measured, particularly for WebAssembly and modern web applications. The benchmark shifts WebAssembly scoring from separate Startup/Runtime phases to a unified approach measuring First Iteration (compilation), Worst Case (jank/GC pauses), and Average Case (throughput) to better reflect real-world usage. The update solves the "infinity problem" where engines became so fast at WebAssembly instantiation that benchmark times rounded to zero milliseconds, creating infinite scores. JetStream 3 moves beyond microbenchmarks to larger, longer-running workloads that prevent engines from over-optimizing for specific patterns and instead optimize for actual developer practices. JavaScriptCore improvements include inlining GC allocations for WasmGC (40% performance gain), restructuring memory layout to eliminate pointer indirection, and optimizing type reference counting to reduce ga

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