Created
December 20, 2023 19:13
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#include <bits/time.h> | |
#include <stdint.h> | |
#include <stdlib.h> | |
#include <stdio.h> | |
#include <sys/types.h> | |
#include <time.h> | |
// https://igoro.com/archive/gallery-of-processor-cache-effects/ | |
u_int64_t now_ns() | |
{ | |
struct timespec ts; | |
clock_gettime(CLOCK_MONOTONIC_RAW, &ts); | |
return ts.tv_sec * (uint64_t)1e9 + ts.tv_nsec; | |
} | |
__inline__ uint64_t rdtsc(void) | |
{ | |
uint32_t lo, hi; | |
__asm__ __volatile__ ( // serialize | |
"xorl %%eax,%%eax \n cpuid" | |
::: "%rax", "%rbx", "%rcx", "%rdx"); | |
/* We cannot use "=A", since this would use %rax on x86_64 and return only the lower 32bits of the TSC */ | |
__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi)); | |
return (uint64_t)hi << 32 | lo; | |
} | |
#define N (1024*1024*64) | |
int main() | |
{ | |
int * array = calloc(sizeof(int), N); | |
for (size_t k = 0; k < 4; ++k) | |
{ | |
uint64_t start = rdtsc(); | |
for (size_t i = 0; i < N; i += 1) | |
{ | |
array[i] *= 3; | |
} | |
uint64_t end = rdtsc(); | |
printf("elapsed: %lu\n", end - start); | |
} | |
free(array); | |
return 0; | |
} |
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