Improve Fast Refresh responsiveness when watching a large number of files #913
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…iles Summary: Following D40829941 (facebook@7191173), where we changed the output of `metro-file-map`'s `build()` to return "live" references to the file system and the Haste module map (rather than snapshots), we no longer require further snapshots to be emitted as part of a change event payload. In fact, `ChangeEvent['snapshotFS']` and `ChangeEvent['moduleMap']` are currently only referenced in test code. Removing them means we don't have to copy potentially large data structures on each emitted change. With ~300k files and ~150k Haste map entries, this amounts to ~200ms more responsive fast refresh - in general this boost will be proportional to the total number of files+Haste modules watched. After this, a `HasteFS` instance is only constructed once, on Metro startup. That clears the way for an alternative (more expensive to initialise) implementation capable of performing lookups through symlinks. Changelog: [Performance] Improve Fast Refresh responsiveness when watching a large number of files. Reviewed By: motiz88 Differential Revision: D42303139 fbshipit-source-id: ebafcc8a698d9a659e4da37a935d4a4e5961fb65
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This pull request was exported from Phabricator. Differential Revision: D42303139 |
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This pull request has been merged in b942eca. |
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Summary:
Following D40829941 (7191173), where we changed the output of
metro-file-map'sbuild()to return "live" references to the file system and the Haste module map (rather than snapshots), we no longer require further snapshots to be emitted as part of a change event payload. In fact,ChangeEvent['snapshotFS']andChangeEvent['moduleMap']are currently only referenced in test code.Removing them means we don't have to copy potentially large data structures on each emitted change.
With ~300k files and ~150k Haste map entries, this amounts to ~200ms more responsive fast refresh - in general this boost will be proportional to the total number of files+Haste modules watched.
After this, a
HasteFSinstance is only constructed once, on Metro startup. That clears the way for an alternative (more expensive to initialise) implementation capable of performing lookups through symlinks.Changelog: [Performance] Improve Fast Refresh responsiveness when watching a large number of files.
Reviewed By: motiz88
Differential Revision: D42303139