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Samuel Karp
e6ca378dcf
When unpacking a layer changeset in applyNaive, encountering an opaque whiteout (.wh..wh..opq) triggers a directory walk to remove files belonging to lower layers. Since files unpacked earlier in the current layer are recorded in unpackedPaths and preserved, interleaved files and opaque whiteouts in the same directory cause repeated walks over the same growing directory, leading to superlinear execution time. Once a directory has been purged of lower-layer files by an opaque whiteout, all existing and subsequent entries in that directory are guaranteed to be in unpackedPaths. Tracking directories that have already processed an opaque whiteout allows subsequent opaque whiteouts for the same directory to return early, restoring linear unpack time. Benchmark results (n=1,000): | Metric | Pre-change | Post-change | Delta | | :--- | :--- | :--- | :--- | | Execution Time | 2,578.8 ms/op | 135.3 ms/op | ~19.1x faster (94.8% reduction) | | Allocated Memory | 200.5 MB/op | 2.3 MB/op | ~86.9x less memory (98.8% reduction) | | Allocs / op | 2,068,820 allocs/op | 48,060 allocs/op | ~43.0x fewer allocs (97.7% reduction) | Assisted-by: Antigravity Signed-off-by: Samuel Karp <samuelkarp@google.com>