We have noticed that Node's spawn() is not asynchronous on Linux with memory RSS more than 16 GB, blocking the event loop for as much as 2 seconds.
The issue comes down to Linux copying the entire RSS each time spawn() is called from the main event loop thread. Moving the call to uv_spawn() to the threadpool would likely fix the issue by not blocking the main event loop thread.If you think you might be affected, there is a short script to reproduce here:
https://github.com/nodejs/node/issues/14917#issuecomment-323697188