听人说gettimeofday 在64bit下有缓存，速度很快，测试下了，感觉不对啊。。
#include <time.h>
#include <sys/time.h>
#include <stdio.h>
#include <stdint.h>
int foo(int i)
{
return i;
}
const int64_t MAX_COUNT = *;
struct TimerEval {
TimerEval(const char* module)
{
start_time_ = time(NULL);
module_ = module;
}
~TimerEval()
{
time_t end_time = time(NULL);
printf("%s\telapse : %d sec\n", module_,
(end_time - start_time_));
}
time_t start_time_;
const char* module_;
};
int main()
{
struct timeval tpTmp;
printf("repeat %d times, test result is : \n", MAX_COUNT);
{
TimerEval eval("call fun");
for (int i=; i<MAX_COUNT; ++i)
foo(i);
}
{
TimerEval eval("call time");
for (int i=; i<MAX_COUNT; ++i)
time(NULL);;
}
{
TimerEval eval("call gettimeofday");
for (int i=; i<MAX_COUNT; ++i)
gettimeofday(&tpTmp, NULL);;
}
{
TimerEval eval("call clock_gettime");
struct timespec tp;
for (int i=; i<MAX_COUNT; ++i)
clock_gettime(CLOCK_REALTIME, &tp);
}
return ;
}
测试结果
repeat 100000000 times, test result is :
call fun elapse : 1 sec
call time elapse : 1 sec
call gettimeofday elapse : 7 sec
call clock_gettime elapse : 15 sec
编译参数
g++ timer_benchmarck.cc -m64 -lrt
貌似事实可能不是这样，求教于大家，可能是什么原因。
如果说time只是在gettimeofday的基础上封装了一层，那怎么time会比gettimeofday还快，不科学啊！
/* Return the current time as a `time_t' and also put it in *T if T is
not NULL. Time is represented as seconds from Jan 1 00:00:00 1970. */
time_t
time (t)
time_t *t;
{
struct timeval tv;
time_t result; if (__gettimeofday (&tv, (struct timezone *) NULL))
result = (time_t) -;
else
result = (time_t) tv.tv_sec;
if (t != NULL)
*t = result;
return result;
}