Draft: Implement watching file paths via oslib.watch
#5068
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…hing # Conflicts: # runner/package.mill
…provement/fs-watching
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What are the CPU numbers on your laptop with this change applied? |
I haven't tested it yet, as my repo uses mill 0.12.10. With #5073 I'll be able to test it and report it later. |
I tested the 0.12.x branch, the CPU now hover's around 0.1%-2.5%, not enough to trigger the CPU fan, whilst previously CPU fan was constantly on. Screencast_20250507_200300.webm |
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…hing # Conflicts: # build.mill # runner/daemon/package.mill # runner/daemon/src/mill/daemon/MillMain.scala
…hing' into improvement/fs-watching
…hing' into improvement/fs-watching
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Currently watching files uses polling which is inefficient with large codebases. On my laptop
./mill --watchuses 20% CPU just to watch the files for changes.This uses
oslib'swatchmodule to watch for the file changes instead of polling them.We had to update oslib (com-lihaoyi/os-lib#386) to:
outor.bloopemits Java FS watcherOVERFLOWevents.println's thatoslib.watchhad.The current approach to watching is to watch the workspace root via FS watching. FS watching only works with folders and we have to watch
root/build.mill, and thus,root/, so everything else falls under it.Mac OS watcher performs watching recursively natively, but on linux oslib adds recursive watches itself, so we use
oslib.watchfilter to prevent watching anything that is not an ancestor of watched root. For example, if we have source atroot/module-a/src/, we'll watchroot/,root/module-a/androot/.Finally, events are filtered so that unrelated changes (like creating
root/random-file.txt) does not trigger reevaluation.The fs watching is enabled by default and can be disabled via
--watch-via-fs-notify=false.0.12.xversion: #5073