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测试alignment对内存访问性能的影响
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#include <iostream> | |
#include <stdint.h> | |
template<typename T> | |
inline void copy_byte(uint8_t* dst, uint8_t* src, size_t size ) { | |
T* sdst = (T*)dst; | |
T* ssrc = (T*)src; | |
size /= sizeof(T); | |
clock_t s = clock(); | |
while (size-- > 0) | |
*sdst++ = *ssrc++; | |
clock_t e = clock(); | |
std::cout << "size:" << sizeof(T) << "," << (e - s) * 1.0/(CLOCKS_PER_SEC) << std::endl; | |
} | |
int main(int argc, char** argv) { | |
const size_t kSize = 1024*1024*100; | |
uint8_t* dst = (uint8_t*) malloc(kSize); | |
uint8_t* src = (uint8_t*) malloc(kSize); | |
std::cout << (void*)dst << std::endl; | |
for (int i = 0; i < 8; i++) { | |
std::cout << (void*)(dst + i) << std::endl; | |
clock_t s = clock(); | |
memcpy(dst + i, src + i, kSize - i); | |
clock_t e = clock(); | |
std::cout << (e - s) * 1.0/CLOCKS_PER_SEC << std::endl; | |
copy_byte<uint8_t>(dst + i, src + i, kSize - i); | |
copy_byte<uint16_t>(dst + i, src + i, kSize - i); | |
copy_byte<uint32_t>(dst + i, src + i, kSize - i); | |
copy_byte<size_t>(dst + i, src + i, kSize - i); | |
} | |
// memcpy(dst + 1, src + 1, kSize - 1); | |
return 0; | |
} | |
/* | |
caoshiweideMacBook-Pro:test caoshiwei$ g++ -O3 alignment.cc | |
caoshiweideMacBook-Pro:test caoshiwei$ ./a.out | |
0x10652f000 | |
0x10652f000 | |
0.099874 | |
size:1,0.017212 | |
size:2,0.016584 | |
size:4,0.025358 | |
size:8,0.017103 | |
0x10652f001 | |
0.015442 | |
size:1,0.025877 | |
size:2,0.016838 | |
size:4,0.017774 | |
size:8,0.021104 | |
0x10652f002 | |
0.01942 | |
size:1,0.025366 | |
size:2,0.019621 | |
size:4,0.025841 | |
size:8,0.018191 | |
0x10652f003 | |
0.020936 | |
size:1,0.022729 | |
size:2,0.023116 | |
size:4,0.029354 | |
size:8,0.022287 | |
0x10652f004 | |
0.022226 | |
size:1,0.023343 | |
size:2,0.023158 | |
size:4,0.017101 | |
size:8,0.022718 | |
0x10652f005 | |
0.021892 | |
size:1,0.023646 | |
size:2,0.025684 | |
size:4,0.019284 | |
size:8,0.026392 | |
0x10652f006 | |
0.019575 | |
size:1,0.021858 | |
size:2,0.024489 | |
size:4,0.025159 | |
size:8,0.023368 | |
0x10652f007 | |
0.018965 | |
size:1,0.026968 | |
size:2,0.01899 | |
size:4,0.025701 | |
size:8,0.020535 | |
*/ | |
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#include <iostream> | |
#include <stdint.h> | |
int main(int argc, char** argv) { | |
const size_t kSize = 1024*1024; | |
uint8_t* mem1 = (uint8_t*) malloc(kSize*sizeof(double)); | |
uint8_t* mem2 = (uint8_t*) malloc(kSize*sizeof(double)); | |
std::cout << (void*) mem1 << "," << (void*) mem2 << std::endl; | |
for (int i = 0; i < kSize*sizeof(double); i++) { | |
mem1[i] = 0; | |
mem2[i] = 0; | |
} | |
double sum = 0; | |
for (int align = 0; align < 8; align++) { | |
double* nums = (double*)(mem1 + align); | |
double* numb = (double*)(mem2 + align); | |
for (int i = 0; i < kSize - 1; i++) { | |
nums[i] = i*random(); | |
numb[i] = i*random(); | |
} | |
clock_t s = clock(); | |
for (int i = 0; i < kSize - 1; i++) { | |
nums[i] = nums[i] * numb[i]; | |
sum += nums[i]; | |
} | |
clock_t e = clock(); | |
std::cout << "align:" << align << "," << (e - s) * 1.0/(CLOCKS_PER_SEC) << std::endl; | |
std::cout << sum << std::endl; | |
} | |
return 0; | |
} | |
/* | |
caoshiweideMacBook-Pro:test caoshiwei$ ./a.out | |
0x10fd9d000,0x11059e000 | |
align:0,0.00296 | |
4.42795e+35 | |
align:1,0.001538 | |
8.86286e+35 | |
align:2,0.003423 | |
1.32945e+36 | |
align:3,0.001611 | |
1.77246e+36 | |
align:4,0.001402 | |
2.21554e+36 | |
align:5,0.00242 | |
2.65889e+36 | |
align:6,0.001776 | |
3.10164e+36 | |
align:7,0.002441 | |
3.5454e+36 | |
*/ | |
/* | |
swcao@swcao-linux:~$ ./a.out | |
0x7f5358757010,0x7f5326756010 | |
align:0,0.38 | |
4.43033e+41 | |
align:1,0.37 | |
8.86186e+41 | |
align:2,0.38 | |
1.32928e+42 | |
align:3,0.37 | |
1.77234e+42 | |
align:4,0.38 | |
2.21538e+42 | |
align:5,0.37 | |
2.65848e+42 | |
align:6,0.38 | |
3.10148e+42 | |
align:7,0.38 | |
3.54458e+42 | |
*/ |
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