Integration of ECMAScript to WebAssembly ahead-of-time compiler js2wasm

[ttraenkler]

@bartlomieju: Following up on our exchange, I would offer to write a POC for js2wasm integration into v8x.

Being an ahead-of-time compiler the expectation would be a smaller footprint and higher performance than QuickJS, allowing for denser packing and reduced runtime costs per function call. WebAssembly would add isolation ideal for a multi-tenant setup.

After looking into it, the idea would be to compile TypeScript to WebAssembly directly, then precompile the .wasm module with Wasmtime to .cwasm for small footprint and fast cold starts and then measure the shared runtime and per instance footprint and performance compared to QuickJS. For even smaller footprint the IR could also be lowered to a native target, but WebAssembly's module sandbox is ideal for multi-tenant setups.

Would that fit into your vision for v8x and how big is the current footprint and performance with QuickJS compared to V8? Are you running native QuickJS or a Wasm build and how do you isolate tenants from each other?

[littledivy]

js2wasm looks really cool! v8x is a compat shim for embedding APIs of different engines, the QuickJS backend is native 1MB binary size footprint. To add js2wasm to v8x, we will need a thin C-ABI exposing JavaScript values and runtime APIs. Wasm sandboxing is a concern for downstream crates that might use v8x like, celld, just orthogonal to implementing the C-ABI.

If you want to take a stab at it, I'd be happy to merge any PRs and add a js2wasm backend with a Cargo feature flag

[ttraenkler]

Thanks @littledivy! Spiked feasibility in #75, confirming the expectation of higher density and throughput. Do you have a test setup I could benchmark against? Otherwise I would try some simple request / response with hono.

[littledivy]

Cool! Can it boot deno_core? We currently use a built Deno for benchmarks - startup time, Deno.serve HTTP throghput and peak RSS.

simple request / response with hono

That works! I imagine it will be a lot of work to get Deno compiling. If it makes life easier, we can merge your initial work as a feature flag

[ttraenkler]

Cool! Can it boot deno_core? We currently use a built Deno for benchmarks - startup time, Deno.serve HTTP throghput and peak RSS.

Not yet, will take some time. Just did the minimal spike.

simple request / response with hono

That works! I imagine it will be a lot of work to get Deno compiling. If it makes life easier, we can merge your initial work as a feature flag

Cool, but I would prefer getting deno_core working first.