clock
#include <ctime>
#include <iostream>
int main() {
clock_t st = clock();
// do something
clock_t ed = clock();
std::cout << ed - st << std::endl;
std::cout << (ed - st) / CLOCKS_PER_SEC << std::endl;
}
high_resolution_clock
可以达到纳秒的精度:
#include <chrono>
#include <iostream>
int main() {
typedef std::chrono::high_resolution_clock Clock;
auto t1 = Clock::now();
// do something
auto t2 = Clock::now();
std::cout << std::chrono::duration_cast<std::chrono::nanoseconds>(t2-t1).count() << '\n';
}
rdtsc/rdtscp
缓存失效的访存时间:
extern u_int64_t test(int *p, int i);
.section .text
.global test
.type test, @function
test:
movslq %esi, %rsi
rdtscp
mov %rax, %r10
sal $32, %rdx
or %rdx, %r10
movslq (%rdi,%rsi,4), %r11
rdtscp
sal $32, %rdx
or %rdx, %rax
sub %r10, %rax
ret