High CPU when using file watchers and volumes

My project (A small, ~8 endpoint express app) uses typescript compiler file watching (tsc --watch) and nodemon for local development.

The combination of these two processes running outside of docker, on MacOS, uses approximately 5% of one CPU core when idle, 25% cpu of one core when compiling/reloading, and finishes in approximately 2 seconds.

We've been experimenting with developing inside of Docker, as an alternative to using Node Version Manager and juggling multiple projects with different node versions.

Here is the example script we have been running:

yarnWatch.sh

#!/bin/sh

tsc --watch
nodemon app.js

docker run \
  --volume $(pwd):/proj \
  --workdir /proj \
  --rm \
  --publish 3030:3030 \
  --detach \
  node:12.16.1-alpine scripts/yarnWatch.sh

When running in this way, the hyperkit process idles at 200% CPU (my guess is 100% of two cores), uses 500%cpu when compiling/relaoding, and finishes in 20 seconds.

My hypothesis is this is some sort of bottleneck regarding volumes, as running the app in a custom built image has no performance problems.

Reproduce the reported setup using yarnWatch.sh, the node:12.16.1-alpine image, and the /proj volume mount from the provided Docker command. Compare idle and reload CPU usage with the custom image that reportedly has no performance problems, then determine whether the volume configuration accounts for the slowdown and document the result.