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make it twice as fast

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lukechampine
2018-07-05 23:29:14 -04:00
parent a04e125b73
commit 000cb373af
2 changed files with 75 additions and 55 deletions
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README.md
+19 -19
View File
@@ -9,7 +9,7 @@ go get github.com/lukechampine/fastxor
```
Is there a gaping hole in your heart that can only be filled by xor'ing byte
streams at 20GB/s? If so, you've come to the right place.
streams at 60GB/s? If so, you've come to the right place.
`fastxor` is exactly what it sounds like: a package that xors bytes as fast
as your CPU is capable of. For best results, use a CPU that supports a SIMD
@@ -25,37 +25,37 @@ my code and let me know how I could make it faster or cleaner!
```
AVX:
BenchmarkBytes/16-4 200000000 8.72 ns/op 1835.82 MB/s
BenchmarkBytes/1024-4 50000000 38.1 ns/op 26850.41 MB/s
BenchmarkBytes/65k-4 500000 2738 ns/op 23930.93 MB/s
BenchmarkBytes/16-4 200000000 6.20 ns/op 2579.65 MB/s
BenchmarkBytes/1024-4 100000000 15.5 ns/op 66089.39 MB/s
BenchmarkBytes/65k-4 2000000 974 ns/op 67217.99 MB/s
SSE:
BenchmarkBytes/16-4 200000000 8.63 ns/op 1852.98 MB/s
BenchmarkBytes/1024-4 50000000 39.4 ns/op 25993.00 MB/s
BenchmarkBytes/65k-4 500000 2733 ns/op 23975.08 MB/s
BenchmarkBytes/16-4 200000000 6.31 ns/op 2536.64 MB/s
BenchmarkBytes/1024-4 50000000 27.2 ns/op 37609.69 MB/s
BenchmarkBytes/65k-4 1000000 2009 ns/op 32619.21 MB/s
Word-wise:
BenchmarkBytes/16-4 100000000 10.5 ns/op 1521.66 MB/s
BenchmarkBytes/1024-4 10000000 125 ns/op 8163.59 MB/s
BenchmarkBytes/65k-4 200000 6895 ns/op 9504.62 MB/s
BenchmarkBytes/16-4 200000000 7.37 ns/op 2170.17 MB/s
BenchmarkBytes/1024-4 20000000 89.4 ns/op 11455.33 MB/s
BenchmarkBytes/65k-4 300000 4963 ns/op 13203.25 MB/s
Byte-wise:
BenchmarkBytes/16-4 100000000 17.3 ns/op 925.16 MB/s
BenchmarkBytes/1024-4 2000000 841 ns/op 1216.31 MB/s
BenchmarkBytes/65k-4 30000 54100 ns/op 1211.38 MB/s
BenchmarkBytes/16-4 100000000 12.7 ns/op 1263.77 MB/s
BenchmarkBytes/1024-4 2000000 610 ns/op 1677.18 MB/s
BenchmarkBytes/65k-4 50000 38906 ns/op 1684.45 MB/s
```
Conclusions: `fastxor` is 2-25 times faster than a naive `for` loop. AVX and
SSE performance is roughly equivalent, which makes me suspect that I may be
doing something wrong. Lastly, for very small slices, the cost of the function
call starts to outweigh the benefit of AVX/SSE (the Go compiler never inlines
handwritten asm). If you need to xor exactly 16 bytes (common in block
Conclusions: `fastxor` is 2-40 times faster than a naive `for` loop. AVX is
roughly twice as fast as SSE, which is unsurpising since it can operate on
twice as many bits per cycle. Lastly, for very small slices, the cost of the
function call starts to outweigh the benefit of AVX/SSE (the Go compiler never
inlines handwritten asm). If you need to xor exactly 16 bytes (common in block
ciphers), the specialized `Block` function outperforms the more generic
`Bytes`:
```
BenchmarkBlock-4 500000000 3.69 ns/op 4337.88 MB/s
BenchmarkBlock-4 1000000000 2.72 ns/op 5888.02 MB/s
```
xor_amd64.s
+56 -36
View File
@@ -116,36 +116,62 @@ TEXT ·xorBytesAVX(SB),NOSPLIT,$0
MOVQ b_data+48(FP), B
MOVQ n+72(FP), N
XOR_LOOP_256_AVX:
CMPQ N, $256
JB XOR_LOOP_128_AVX
VMOVDQU (A), Y0
VMOVDQU 32(A), Y1
VMOVDQU 64(A), Y2
VMOVDQU 96(A), Y3
VMOVDQU 128(A), Y4
VMOVDQU 160(A), Y5
VMOVDQU 192(A), Y6
VMOVDQU 224(A), Y7
VPXOR (B), Y0, Y0
VPXOR 32(B), Y1, Y1
VPXOR 64(B), Y2, Y2
VPXOR 96(B), Y3, Y3
VPXOR 128(B), Y4, Y4
VPXOR 160(B), Y5, Y5
VPXOR 192(B), Y6, Y6
VPXOR 224(B), Y7, Y7
VMOVDQU Y0, (Dst)
VMOVDQU Y1, 32(Dst)
VMOVDQU Y2, 64(Dst)
VMOVDQU Y3, 96(Dst)
VMOVDQU Y4, 128(Dst)
VMOVDQU Y5, 160(Dst)
VMOVDQU Y6, 192(Dst)
VMOVDQU Y7, 224(Dst)
ADDQ $256, A
ADDQ $256, B
ADDQ $256, Dst
SUBQ $256, N
JNZ XOR_LOOP_256_AVX
RET
XOR_LOOP_128_AVX:
CMPQ N, $128
JB XOR_LOOP_64_AVX
VMOVDQU (A), X0
VMOVDQU 16(A), X1
VMOVDQU 32(A), X2
VMOVDQU 48(A), X3
VMOVDQU 64(A), X4
VMOVDQU 80(A), X5
VMOVDQU 96(A), X6
VMOVDQU 112(A), X7
VMOVDQU (A), Y0
VMOVDQU 32(A), Y1
VMOVDQU 64(A), Y2
VMOVDQU 96(A), Y3
VPXOR (B), X0, X0
VPXOR 16(B), X1, X1
VPXOR 32(B), X2, X2
VPXOR 48(B), X3, X3
VPXOR 64(B), X4, X4
VPXOR 80(B), X5, X5
VPXOR 96(B), X6, X6
VPXOR 112(B), X7, X7
VPXOR (B), Y0, Y0
VPXOR 32(B), Y1, Y1
VPXOR 64(B), Y2, Y2
VPXOR 96(B), Y3, Y3
VMOVDQU X0, (Dst)
VMOVDQU X1, 16(Dst)
VMOVDQU X2, 32(Dst)
VMOVDQU X3, 48(Dst)
VMOVDQU X4, 64(Dst)
VMOVDQU X5, 80(Dst)
VMOVDQU X6, 96(Dst)
VMOVDQU X7, 112(Dst)
VMOVDQU Y0, (Dst)
VMOVDQU Y1, 32(Dst)
VMOVDQU Y2, 64(Dst)
VMOVDQU Y3, 96(Dst)
ADDQ $128, A
ADDQ $128, B
@@ -158,20 +184,14 @@ XOR_LOOP_64_AVX:
CMPQ N, $64
JB XOR_LOOP_16_AVX
MOVOU (A), X0
MOVOU 16(A), X1
MOVOU 32(A), X2
MOVOU 48(A), X3
VMOVDQU (A), Y0
VMOVDQU 32(A), Y1
VPXOR (B), X0, X4
VPXOR 16(B), X1, X5
VPXOR 32(B), X2, X6
VPXOR 48(B), X3, X7
VPXOR (B), Y0, Y2
VPXOR 32(B), Y1, Y3
VMOVDQU X4, (Dst)
VMOVDQU X5, 16(Dst)
VMOVDQU X6, 32(Dst)
VMOVDQU X7, 48(Dst)
VMOVDQU Y2, (Dst)
VMOVDQU Y3, 32(Dst)
ADDQ $64, A
ADDQ $64, B