Wasm doesn't work in limited virtual memory situations

[emspishak]

Version

v22.13.0

Platform

Linux weborigin002 6.1.0-26-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.112-1 (2024-09-30) x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

1. ulimit -v 2097152
2. node -e "await fetch('https://www.google.com')"

How often does it reproduce? Is there a required condition?

Everytime, no required conditions.

What is the expected behavior? Why is that the expected behavior?

I expect the fetch to succeed.

What do you see instead?

The fetch fails with the error:

node:internal/deps/undici/undici:5822
      return await WebAssembly.instantiate(mod, {
                               ^

RangeError: WebAssembly.instantiate(): Out of memory: Cannot allocate Wasm memory for new instance
    at lazyllhttp (node:internal/deps/undici/undici:5822:32)

Node.js v22.13.0

Additional information

I would like to run a Node server on a shared webhost, which has per-user memory limitations to prevent one (or multiple) users from consuming too much memory. The configuration they use is ulimit -v 2097152 to limit virtual memory to about 2GB. Node Wasm seems to allocate around 10GB of virtual memory, which fails when memory is limited in this way. 2GB seems like a reasonable amount of memory and it seems like Node should support it. I asked my hosting provider if they could bump up the memory limit and they said they don't want to.

I started looking through the code for this, starting at

node/deps/v8/src/wasm/module-instantiate.cc

Line 2557 in 187007a

MaybeHandle<WasmMemoryObject> maybe_memory_object = WasmMemoryObject::New(

I found the --wasm_max_mem_pages command line flag, but even with --wasm_max_mem_pages=2 it still tries to allocate 10GB.

It appears to be the reservation_size at

node/deps/v8/src/objects/backing-store.cc

Line 337 in 7a9d783

size_t reservation_size =

that ends up being 10GB. That looks like it's coming from

node/deps/v8/src/objects/backing-store.cc

Line 96 in 7a9d783

return kFullGuardSize32;

where it just always returns 10GB.

So it seems like maybe there it could detect how much memory is available and base the amount it returns off that (some percentage of it so it keeps free memory for other things too?). I'm happy to send a PR for this but would appreciate some help figuring out how this should work.

Thank you!

[emspishak]

My hosting provider pointed me to https://nodejs.org/api/cli.html#--disable-wasm-trap-handler, which seems like the best we could probably do here. Reading through #52766 and (especially) https://docs.google.com/document/d/1PM4Zqmlt8ac5O8UNQfY7fOsem-6MhbsB-vjFI-9XK6w/edit?usp=sharing helped me understand more of the context.