WASM Heap allocated never cleared

• WASM Heap allocated never cleared
  • Dropping memory
  • Allocator freed pages

Dropping memory

Make sure your code is dropping memory. WASM lets you reallocate memory, so you need to drop the memory in your code.

struct X(u32);

impl X {
    fn drop(self) {}
}

fn main() {
    let x = X(10);

    // Usually x goes out of scope and would get dropped.
    // But we can drop it here to profile memory.
    // Remember the allocation of WASM happens in chunks so
    // we want to see if we be deallocating appropriately for reuse 
    // by watching if a memory growth happens
    x.drop();
}

Allocator freed pages

Some allocators can be optimized to not return freed pages to the WebAssembly engine/operating system. Make sure your allocator is reallocating appropriate to your needs. Rust default allocator allows reuse of memory with WebAssembly, for example.