Benchmarks

Why xxhash64?

The fingerprint detects file content changes — it does not protect against attackers. xxhash64 is a non-cryptographic hash that is ~11x faster than SHA-256, zero allocations, and hits ~27 GB/s throughput.

Results

xxhash64 vs crypto/sha256 — 100K iterations per benchmark, single core.

Hardware: AMD Ryzen AI MAX+ 395, Go 1.26.3, linux/amd64

Hash	Size	ns/op	Throughput	Allocations
xxhash64	1 KB	42	24,443 MB/s	0
SHA-256	1 KB	486	2,106 MB/s	1 × 32 B
xxhash64	10 KB	383	26,708 MB/s	0
SHA-256	10 KB	4,253	2,408 MB/s	1 × 32 B
xxhash64	100 KB	3,744	27,349 MB/s	0
SHA-256	100 KB	41,760	2,452 MB/s	1 × 32 B
xxhash64	1 MB	37,954	27,628 MB/s	0
SHA-256	1 MB	429,268	2,443 MB/s	1 × 32 B

xxhash64 is ~11x faster than SHA-256, zero allocations, and hits ~27 GB/s — effectively RAM bandwidth. No hardware accelerator exists or is needed; the hash is memory-bound, not compute-bound. SHA-256 results already include SHA-NI hardware acceleration.

Reproducing

go test -bench=. -benchmem -benchtime=100000x

Interpretation

At ~27 GB/s, the hash is memory-bound — it runs at the speed of RAM. The CPU spends most of its time waiting for memory, not computing. This means:

• Fingerprinting a 1 MB config file: ~38 microseconds
• Fingerprinting a 10 KB config file: ~383 nanoseconds
• Zero heap allocations — no GC pressure

For a read-modify-write cycle, the fingerprint adds negligible overhead compared to the I/O of reading and writing the file itself.