metro-file-map: Spawn fewer workers for smaller workloads #1439
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Summary: This error message isn't accurate since Metro added symlink support, and doesn't suggest the most likely cause, which is that the requested file isn't watched. Metro's resolver should never resolve an unwatched file, but custom resolvers (like `rnx-kit`'s) might. Changelog: Internal Reviewed By: vzaidman Differential Revision: D69397742
Summary: `metro-file-map` currently spins up `maxWorkers` workers (processes, or threads if `enableWorkerThreads`) for any batch workload. `maxWorkers` is `os.availableParallelism` by default. When we have a warm cache or Saved State, we may only have a handful of changed files to process, and frequently create more workers than we have files. This implements a simple heuristic factor `maxFilesPerWorker`, such that we use `Math.ceil(numFiles/maxFilesPerWorker)` parallelism (where 1 "worker" means we process in-band). The default value of 100 is somewhat finger-in-air as a bunch of factors would determine the optimal value - including threads or not, which host platform, and computational cost of the haste impl and dependency extraction. We could expose this as Metro configuration in future. Changelog: - **[Performance]** Don't start an excessive number of workers for hashing files during startup. Differential Revision: D69704168
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Summary:
metro-file-mapcurrently spins upmaxWorkersworkers (processes, or threads ifenableWorkerThreads) for any batch workload.maxWorkersisos.availableParallelismby default.When we have a warm cache or Saved State, we may only have a handful of changed files to process, and frequently create more workers than we have files.
This implements a simple heuristic factor
maxFilesPerWorker, such that we useMath.ceil(numFiles/maxFilesPerWorker)parallelism (where 1 "worker" means we process in-band).The default value of 100 is somewhat finger-in-air as a bunch of factors would determine the optimal value - including threads or not, which host platform, and computational cost of the haste impl and dependency extraction. We could expose this as Metro configuration in future.
Changelog:
Differential Revision: D69704168