Memory Used By Wasm · wasmtime · Zulip Chat Archive

What would be the best way to get memory currently used by the wasm? Right now the only thing that comes into my mind is subtracting the last offset I get from my wasm program from the base pointer of the data

Lann Martin (Mar 10 2023 at 16:45):

From the guest or the host?

Cwasi4wasm (Mar 10 2023 at 17:21):

This would be from the host. Interested in the size of the current mem used by my wasm sandbox

Lann Martin (Mar 10 2023 at 18:51):

I have this snippet, which sums the size of linear memories owned by a wasmtime::Instance

    let memories = instance
        .exports(&mut store)
        .flat_map(|export| export.into_memory())
        .collect::<Vec<_>>();
    let memory_used = &memories
        .into_iter()
        .map(|mem| mem.size(&store))
        .sum::<u64>();

Lann Martin (Mar 10 2023 at 18:51):

I don't recall exactly why it has to be so convoluted... maybe because of how it borrows store? :thinking:

Lann Martin (Mar 10 2023 at 18:55):

Oh and that count is wasm pages, so * 64KB for bytes

Cwasi4wasm (Mar 10 2023 at 19:01):

thank you for the code! Very sorry I didn't explain it properly. Not looking for the page size but memory in use by the sandbox so I guess this would be less than or equal to the size of the sandbox

Lann Martin (Mar 10 2023 at 19:07):

There isn't one clear answer to your question. Some of the resources used by an instance will be shared across all instances or all instances of a single module.