How much memory should swc watch consume?

[ruscon]

I am currently testing how much memory tsc and swc use in watch mode.

What I am using:
macos
docker desktop
docker compose watch with sync action
node:22.7.0-bookworm-slim
pnpm 9.9.0

"@swc/cli": "0.4.0",
"@swc/core": "1.7.21",
"@swc/jest": "0.2.36",
"@swc/plugin-transform-imports": "3.0.1",
"typescript": "5.6.1-rc"

Let's say I have a monorepo with 2 subprojects and 30 small ts files in total.

• swc uses memory more smoothly in total, about ~390mb on start, then frees up memory up to ~350mb after ~1min.

• tsc works with large peaks, reaching ~130mb on start, ~275mb after any changes in file (even more after several successive changes), then frees up memory up to ~110mb after ~1min. tsc also loads the processor more with peaks.

All numbers without running node process and taken from docker stats.
exclude options configured in both cases, even node_modules folders deleted, for the sake of the purity of the experiment.

how I run swc

pnpm exec swc ./packages/*/src --config-file .swcrc -d ./dist --only **/*.ts -w --log-watch-compilation

how I run tsc (composite with 2 subprojects)

pnpm exec tsc -b tsconfig.build.json --noCheck -w --preserveWatchOutput --pretty

The question is, should swc really use so much memory for 30 files? I assumed that it would be at least a couple of times less than tsc.

The question is, can someone share their conclusions about a similar kind of testing in watch mode?

UPDATE

after further research I found a couple of bottlenecks.
pnpm exec and npx gives additional overhead on memory, better to run the command directly from node_modules:

• running the command via npx

  • swc: uses ~345mb of memory on start, on file change no change in memory consumption and ~330mb after 1min of inaction
  • tsc: uses ~80mb of memory on start, ~220mb on file change and ~85mb after 1min of inaction.

• running the command directly from node_modules:

  • swc: uses ~310mb of memory on start, on file change and after 1min of inaction there is no change in memory consumption
    • If run swc with --workers 1 it consumes less memory: ~195mb on start (directly from node_modules), on file change and after 1min of inaction there is no change in memory consumption
  • tsc: uses ~50mb of memory on start, ~200mb on file change and ~60mb after 1min of inaction
    • without --noCheck uses ~200mb of memory on start, ~300mb on file change and ~65mb after 1min of inaction

The rest of the memory consumption is probably due to the chokidar library.
Found an interesting topic vitejs/vite#13593
It might be worthwhile to stop using chokidar and use @parcel/watcher instead.