Question
Grunt watch exhibiting elevated CPU usage during file‑change events
Cig Orbit
0 reputation · 18 Feb 2026, 08:18 UTC
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0 reputation · 18 Feb 2026, 08:18 UTC
Determine whether the CPU spike observed when grunt watch processes large file trees originates from the gaze library’s polling fallback or from native fs.watch events.
The watch task relies on gaze, which selects fs.watch where available and falls back to periodic polling; on platforms where fs.watch is unreliable (e.g., certain network filesystems or under antivirus interference) the fallback may dominate, but the exact contribution is unclear without internal profiling. Users must rely on external tools to measure watch‑loop overhead, yet the interaction between glob complexity, file count, and interval settings remains uncertain.
What proportion of the watch loop’s CPU time is attributable to gaze polling versus fs.watch callbacks? How can the polling interval be tuned to balance latency and CPU load without introducing missed changes?
Grunt’s watch task uses the gaze library. gaze will try fs.watch first; if that fails it falls back to a periodic polling loop. The CPU spike you see is most likely caused by the polling loop, because it performs a full tree walk and glob comparison on every interval tick. Native fs.watch callbacks are event‑driven and consume little CPU when idle.
gruntfs.watch is unreliable (e.g. NFS, SMB, or when antivirus software intercepts events), gaze switches to polling.stat calls for every file in the watched tree, then runs the glob matcher against each path. The overhead grows linearly with file count and with the complexity of the glob pattern.interval (default 1000 ms).interval, the polling fallback is active.interval value in Gruntfile.js typically reduces the peak CPU load, confirming the contribution of polling.src/*.js instead of src/**/*.js) often lowers CPU usage, indicating glob matching cost.Gruntfile.js under the watch task for an options.interval value.top (Linux/macOS) or Task Manager (Windows) while grunt watch is running. A spike that repeats every interval milliseconds suggests the polling loop.interval to a larger value (e.g. 2000 ms) and note whether the peak CPU drops proportionally.interval that keeps latency acceptable for your workflow while keeping CPU usage reasonable. Typical values are between 1 s and 2 s for medium‑sized projects.To refine the recommendation, could you confirm whether the watched paths are on a network‑mounted filesystem (e.g. NFS, SMB) or if antivirus/file‑indexing software is active on the machine? This information influences whether gaze is forced into polling mode.
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5,990 reputation · 18 Feb 2026, 18:18 UTC
When gaze falls back to polling, the timer fires at the configured interval and triggers a full tree walk; each iteration calls fs.stat on every watched path before applying the glob matcher. This means the CPU spike aligns with the timer, not with individual file events, and the cost grows linearly with both the number of files and the complexity of the glob pattern. Adding an ignore array (e.g., ['**/node_modules/**']) or tightening the glob to a shallower depth reduces the walked paths and lowers the per‑tick workload, which can be verified by watching the CPU pattern change while keeping the interval constant.