wasm memory snapshot

[seanavery]

Goal:

1. At the end of each block snapshot memory and save to disk.
2. At the beginning of each block, rehydrate wasm vm with the previous memory snapshot

Resources

1. How to overwrite wasm memory https://stackoverflow.com/questions/55921774/share-webassembly-memory-between-module-instances
2. wasm-persist https://github.com/dfinity/wasm-persist/blob/master/index.js

[seanavery]

Strategy 1:

Add javascript to the emscripten module output that handles initializes with a certain memory buffer.

This can be achieved using the --pre-js flag to add javascript code to the js output.

https://emscripten.org/docs/tools_reference/emcc.html#emcc-pre-js

https://emscripten.org/docs/api_reference/module.html#id1

[seanavery]

Should be able to replace memory buffer using Module.buffer

https://emscripten.org/docs/api_reference/module.html#Module.buffer

[seanavery]

Strategy 2:

Simply use c++ delete to garbage collect the class

c++ delete
embind delete

[seanavery]

Strategy 3:

Replace module instance memory. Each module can point to n memories

1-n memory