Tu Dinh Ngoc
b82c016264
tun: use add-with-carry in checksumNoFold()
Use parallel summation with native byte order per RFC 1071.
add-with-carry operation is used to add 4 words per operation. Byteswap
is performed before and after checksumming for compatibility with old
`checksumNoFold()`. With this we get a 30-80% speedup in `checksum()`
depending on packet sizes.
Add unit tests with comparison to a per-word implementation.
**Intel(R) Xeon(R) Silver 4210R CPU @ 2.40GHz**
| Size | OldTime | NewTime | Speedup |
|------|---------|---------|----------|
| 64 | 12.64 | 9.183 | 1.376456 |
| 128 | 18.52 | 12.72 | 1.455975 |
| 256 | 31.01 | 18.13 | 1.710425 |
| 512 | 54.46 | 29.03 | 1.87599 |
| 1024 | 102 | 52.2 | 1.954023 |
| 1500 | 146.8 | 81.36 | 1.804326 |
| 2048 | 196.9 | 102.5 | 1.920976 |
| 4096 | 389.8 | 200.8 | 1.941235 |
| 8192 | 767.3 | 413.3 | 1.856521 |
| 9000 | 851.7 | 448.8 | 1.897727 |
| 9001 | 854.8 | 451.9 | 1.891569 |
**AMD EPYC 7352 24-Core Processor**
| Size | OldTime | NewTime | Speedup |
|------|---------|---------|----------|
| 64 | 9.159 | 6.949 | 1.318031 |
| 128 | 13.59 | 10.59 | 1.283286 |
| 256 | 22.37 | 14.91 | 1.500335 |
| 512 | 41.42 | 24.22 | 1.710157 |
| 1024 | 81.59 | 45.05 | 1.811099 |
| 1500 | 120.4 | 68.35 | 1.761522 |
| 2048 | 162.8 | 90.14 | 1.806079 |
| 4096 | 321.4 | 180.3 | 1.782585 |
| 8192 | 650.4 | 360.8 | 1.802661 |
| 9000 | 706.3 | 398.1 | 1.774177 |
| 9001 | 712.4 | 398.2 | 1.789051 |
Signed-off-by: Tu Dinh Ngoc <dinhngoc.tu@irit.fr>
[Jason: simplified and cleaned up unit tests]
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2025-05-05 15:10:08 +02:00
..
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