40 lines
1.8 KiB
Markdown
40 lines
1.8 KiB
Markdown
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# Measurement: the request path without waste
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- Date: 2026-09-22
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- Machine: AMD Ryzen AI Max+ Pro 395 (32 threads), otherwise idle
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- Toolchain: go1.27.1, no build flags
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- Command: `go test ./internal/nfs4server/ -run '^$' -bench=Wire -benchmem -count=5`
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## Baseline
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The commit c50cd0b, measured in the same session as the new code, both sides
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five runs back to back. The baseline is the wire baseline of
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[2026-09-22-wire-baseline.md](2026-09-22-wire-baseline.md) plus the client
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file commands.
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## Result
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Median of five runs per side, one session.
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| Benchmark | Latency old | Latency new | Change | Allocs old | Allocs new | Change |
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|---|---|---|---|---|---|---|
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| `BenchmarkWireRead64K` | 92.0 µs | 81.5 µs | -11.4 % | 78 | 63 | -19 % |
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| `BenchmarkWireWrite64K` | 61.4 µs | 72.2 µs | see note | 76 | 62 | -18 % |
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| `BenchmarkWireGetattr` | 14.2 µs | 13.5 µs | -4.5 % | 85 | 70 | -18 % |
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| `BenchmarkWireLookup` | 15.2 µs | 15.3 µs | 0 % | 81 | 66 | -19 % |
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Bytes per operation fell 27 percent on READ and 13 percent on WRITE. The
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changes behind the numbers: the COMPOUND answer accumulates in one buffer
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with the header patched in place instead of copying every operation result
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twice, READ fills the reply buffer through the backend's `ReadInto` instead
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of an intermediate allocation and drops the second attribute call for the
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end of file flag, WRITE hands the request record's own bytes to the backend
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instead of copying them out, and the outgoing record marking buffers recycle
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through a bounded pool.
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The WRITE latency column carries an honest warning: the machine's session to
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session variance on this benchmark exceeds the effect being measured. Within
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a single session the order of the two sides flipped twice; the deterministic
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counters, allocations and bytes, are the trustworthy part of the WRITE row,
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and the READ row's improvement is well outside the noise.
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