linux精确分析函数运行时间

网上大部分用clock函数，在线程中计算某个函数运行时间，很不精确

#ifndef PROFILER_H
#define PROFILER_H


#include <time.h>
#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>

class profiler
{

public:
    profiler(const char* func_name)
    {
        gettimeofday(&tv, NULL);
        m_func_name = func_name;
    }


    ~profiler()
    {
        struct timeval tv2;
        gettimeofday(&tv2, NULL);
        long cost = (tv2.tv_sec - tv.tv_sec) * 1000000 + (tv2.tv_usec - tv.tv_usec);
        printf("[%s]cost=%d ms\n", m_func_name, cost / 1000);
    }

private:
    struct timeval tv;
    const char * m_func_name;
};



#define PROFILER() profiler ____profiler_instance##__LINE__(__FUNCTION__)




#endif // PROFILER_H
           

不精确的做法：

static clock_t m_cockStart;
void closkStart()
{
    m_cockStart = clock();
}

void clockFinish(const char* msg)
{
    clock_t finish;
    double total_time;
    finish = clock();
    total_time = (double)(finish-m_cockStart) / CLOCKS_PER_SEC;
    printf( "%s:%f seconds\n", msg, total_time);
}