feat: full NFSv4.2 server and client in pure Go

Assisted-by: GLM 5.3 Flash
2026-09-21 18:51:17 +02:00
commit a9b8039ef7
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+# Measurement: the descriptor cache in internal/nfsfs
+
+- Date: 2026-09-22
+- Machine: AMD Ryzen AI Max+ Pro 395 (32 threads), idle
+- Toolchain: go1.27.1, no build flags
+- Command: `go test ./internal/nfsfs/ -run '^$' -bench=. -benchmem -count=5`
+
+## Baseline
+
+The commit b8758b7, the head of development before the descriptor cache: every
+READ, WRITE and SYNC opened the registered path, verified it with a stat and
+closed the descriptor again, per operation. The cache keeps idle descriptors of
+regular files in a bounded LRU and revalidates the identity on every use, so the
+measurements answer one question: what the open and close per operation cost.
+
+## Result
+
+Median of five runs, same session, same machine.
+
+| Benchmark | Baseline | With cache | Change |
+|---|---|---|---|
+| `BenchmarkRead64K` | 10888 ns/op | 9047 ns/op | -16.9 % |
+| `BenchmarkWrite64K` | 5881 ns/op | 5236 ns/op | -11.0 % |
+| `BenchmarkGetattr` | 461.4 ns/op | 437.2 ns/op | -5.2 % |
+| `BenchmarkLookup` | 1216 ns/op | 1134 ns/op | -6.7 % |
+
+The two data operations are the ones the cache touches, and they gain 11 to 17
+percent per operation. GETATTR and LOOKUP run the same code as before the cache
+(they resolve paths through Lstat either way), so their shifts are code layout
+noise of the same binary, not an effect to claim; both sit within the run to run
+spread the five repetitions showed.