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tun: unwind summing loop in checksumNoFold()

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$ benchstat old.txt new.txt
goos: linux
goarch: amd64
pkg: golang.zx2c4.com/wireguard/tun
cpu: 12th Gen Intel(R) Core(TM) i5-12400
                 │   old.txt    │               new.txt               │
                 │    sec/op    │   sec/op     vs base                │
Checksum/64-12     10.670n ± 2%   4.769n ± 0%  -55.30% (p=0.000 n=10)
Checksum/128-12    19.665n ± 2%   8.032n ± 0%  -59.16% (p=0.000 n=10)
Checksum/256-12     37.68n ± 1%   16.06n ± 0%  -57.37% (p=0.000 n=10)
Checksum/512-12     76.61n ± 3%   32.13n ± 0%  -58.06% (p=0.000 n=10)
Checksum/1024-12   160.55n ± 4%   64.25n ± 0%  -59.98% (p=0.000 n=10)
Checksum/1500-12   231.05n ± 7%   94.12n ± 0%  -59.26% (p=0.000 n=10)
Checksum/2048-12    309.5n ± 3%   128.5n ± 0%  -58.48% (p=0.000 n=10)
Checksum/4096-12    603.8n ± 4%   257.2n ± 0%  -57.41% (p=0.000 n=10)
Checksum/8192-12   1185.0n ± 3%   515.5n ± 0%  -56.50% (p=0.000 n=10)
Checksum/9000-12   1328.5n ± 5%   564.8n ± 0%  -57.49% (p=0.000 n=10)
Checksum/9001-12   1340.5n ± 3%   564.8n ± 0%  -57.87% (p=0.000 n=10)
geomean             185.3n        77.99n       -57.92%

Reviewed-by: Adrian Dewhurst <adrian@tailscale.com>
Signed-off-by: Jordan Whited <jordan@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jordan Whited 2023-10-02 14:43:56 -07:00 committed by Jason A. Donenfeld
parent 4201e08f1d
commit 895d6c23cd
2 changed files with 123 additions and 12 deletions
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100
tun/checksum.go
View File

@ -3,23 +3,99 @@ package tun
import "encoding/binary"
// TODO: Explore SIMD and/or other assembly optimizations.
// TODO: Test native endian loads. See RFC 1071 section 2 part B.
func checksumNoFold(b []byte, initial uint64) uint64 {
ac := initial
i := 0
n := len(b)
for n >= 4 {
ac += uint64(binary.BigEndian.Uint32(b[i : i+4]))
n -= 4
i += 4
for len(b) >= 128 {
ac += uint64(binary.BigEndian.Uint32(b[:4]))
ac += uint64(binary.BigEndian.Uint32(b[4:8]))
ac += uint64(binary.BigEndian.Uint32(b[8:12]))
ac += uint64(binary.BigEndian.Uint32(b[12:16]))
ac += uint64(binary.BigEndian.Uint32(b[16:20]))
ac += uint64(binary.BigEndian.Uint32(b[20:24]))
ac += uint64(binary.BigEndian.Uint32(b[24:28]))
ac += uint64(binary.BigEndian.Uint32(b[28:32]))
ac += uint64(binary.BigEndian.Uint32(b[32:36]))
ac += uint64(binary.BigEndian.Uint32(b[36:40]))
ac += uint64(binary.BigEndian.Uint32(b[40:44]))
ac += uint64(binary.BigEndian.Uint32(b[44:48]))
ac += uint64(binary.BigEndian.Uint32(b[48:52]))
ac += uint64(binary.BigEndian.Uint32(b[52:56]))
ac += uint64(binary.BigEndian.Uint32(b[56:60]))
ac += uint64(binary.BigEndian.Uint32(b[60:64]))
ac += uint64(binary.BigEndian.Uint32(b[64:68]))
ac += uint64(binary.BigEndian.Uint32(b[68:72]))
ac += uint64(binary.BigEndian.Uint32(b[72:76]))
ac += uint64(binary.BigEndian.Uint32(b[76:80]))
ac += uint64(binary.BigEndian.Uint32(b[80:84]))
ac += uint64(binary.BigEndian.Uint32(b[84:88]))
ac += uint64(binary.BigEndian.Uint32(b[88:92]))
ac += uint64(binary.BigEndian.Uint32(b[92:96]))
ac += uint64(binary.BigEndian.Uint32(b[96:100]))
ac += uint64(binary.BigEndian.Uint32(b[100:104]))
ac += uint64(binary.BigEndian.Uint32(b[104:108]))
ac += uint64(binary.BigEndian.Uint32(b[108:112]))
ac += uint64(binary.BigEndian.Uint32(b[112:116]))
ac += uint64(binary.BigEndian.Uint32(b[116:120]))
ac += uint64(binary.BigEndian.Uint32(b[120:124]))
ac += uint64(binary.BigEndian.Uint32(b[124:128]))
b = b[128:]
}
for n >= 2 {
ac += uint64(binary.BigEndian.Uint16(b[i : i+2]))
n -= 2
i += 2
if len(b) >= 64 {
ac += uint64(binary.BigEndian.Uint32(b[:4]))
ac += uint64(binary.BigEndian.Uint32(b[4:8]))
ac += uint64(binary.BigEndian.Uint32(b[8:12]))
ac += uint64(binary.BigEndian.Uint32(b[12:16]))
ac += uint64(binary.BigEndian.Uint32(b[16:20]))
ac += uint64(binary.BigEndian.Uint32(b[20:24]))
ac += uint64(binary.BigEndian.Uint32(b[24:28]))
ac += uint64(binary.BigEndian.Uint32(b[28:32]))
ac += uint64(binary.BigEndian.Uint32(b[32:36]))
ac += uint64(binary.BigEndian.Uint32(b[36:40]))
ac += uint64(binary.BigEndian.Uint32(b[40:44]))
ac += uint64(binary.BigEndian.Uint32(b[44:48]))
ac += uint64(binary.BigEndian.Uint32(b[48:52]))
ac += uint64(binary.BigEndian.Uint32(b[52:56]))
ac += uint64(binary.BigEndian.Uint32(b[56:60]))
ac += uint64(binary.BigEndian.Uint32(b[60:64]))
b = b[64:]
}
if n == 1 {
ac += uint64(b[i]) << 8
if len(b) >= 32 {
ac += uint64(binary.BigEndian.Uint32(b[:4]))
ac += uint64(binary.BigEndian.Uint32(b[4:8]))
ac += uint64(binary.BigEndian.Uint32(b[8:12]))
ac += uint64(binary.BigEndian.Uint32(b[12:16]))
ac += uint64(binary.BigEndian.Uint32(b[16:20]))
ac += uint64(binary.BigEndian.Uint32(b[20:24]))
ac += uint64(binary.BigEndian.Uint32(b[24:28]))
ac += uint64(binary.BigEndian.Uint32(b[28:32]))
b = b[32:]
}
if len(b) >= 16 {
ac += uint64(binary.BigEndian.Uint32(b[:4]))
ac += uint64(binary.BigEndian.Uint32(b[4:8]))
ac += uint64(binary.BigEndian.Uint32(b[8:12]))
ac += uint64(binary.BigEndian.Uint32(b[12:16]))
b = b[16:]
}
if len(b) >= 8 {
ac += uint64(binary.BigEndian.Uint32(b[:4]))
ac += uint64(binary.BigEndian.Uint32(b[4:8]))
b = b[8:]
}
if len(b) >= 4 {
ac += uint64(binary.BigEndian.Uint32(b))
b = b[4:]
}
if len(b) >= 2 {
ac += uint64(binary.BigEndian.Uint16(b))
b = b[2:]
}
if len(b) == 1 {
ac += uint64(b[0]) << 8
}
return ac
}

35
tun/checksum_test.go Normal file
View File

@ -0,0 +1,35 @@
package tun
import (
"fmt"
"math/rand"
"testing"
)
func BenchmarkChecksum(b *testing.B) {
lengths := []int{
64,
128,
256,
512,
1024,
1500,
2048,
4096,
8192,
9000,
9001,
}
for _, length := range lengths {
b.Run(fmt.Sprintf("%d", length), func(b *testing.B) {
buf := make([]byte, length)
rng := rand.New(rand.NewSource(1))
rng.Read(buf)
b.ResetTimer()
for i := 0; i < b.N; i++ {
checksum(buf, 0)
}
})
}
}