I've been running into an issue with Emscripten, where I cannot use a shared WebAssembly.Memory (ie., backed by a SharedArrayBuffer) in a single-threaded build. The rationale for this is to be able to use the Emscripten heap as a shared state with other workers / the UI thread. Specifically, it would allow us to directly copy data to the heap in other threads, avoiding to copy data.
Our scenario looks like this: (1) We run a (single-threaded) WebAssembly module in a worker in a long-running synchronous call; (2) From within the synchronous call stack, the wasm module calls into JS to dispatch some work to the UI thread; (3) We currently COPY the data from the WebAssembly.Memory heap to a separate SharedArrayBuffer, which we then postMessage to the main thread. (4) The worker then uses a wait/notify pattern to block the Emscripten call stack until the UI thread has passed back a result on the SharedArrayBuffer (5) The UI thread can meanwhile perform some asynchronous work (eg., IndexedDB, etc.) and store the response in the SharedArrayBuffer, then notify the waiting worker. (6) The waiting worker then has to COPY the result from the SharedArrayBuffer back onto the Emscripten heap and return. In effect, we're performing two (expensive) copies. If the Emscripten heap was using a SharedArrayBuffer, we could trivially share that with the UI thread and merely pass offsets on the heap around. So in summary, are there any plans to supporting an SAB-backed WebAssembly.Memory for scenarios like these? I understand that a multi-threaded build could accomplish this. However, the extra complexity of the WebAssembly threading model (especially when running the WebAssembly module inside a worker) is not really acceptable in this case. Soeren -- You received this message because you are subscribed to the Google Groups "emscripten-discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/emscripten-discuss/283659cd-4e07-4913-a185-e4e9495f8d12n%40googlegroups.com.
