进程中多个线程的 perf_event

问题描述

我正在尝试使用 perf 分析给定进程中的多个线程。尽管在下面的代码中确实出现，即使 pid 的 perf_event_open 参数是 0（这应该导致对整个过程进行分析？），硬件计数器值仅对应到执行线程（相对于进程内跨线程求和的性能计数器），inf_loop 未计算在内。

我的问题是：如何分析进程中的所有线程与仅执行 perf_event_open 的线程，如下所示？ perf_event_attr 中是否还有其他一些配置需要设置以启用进程范围的分析？

static long perf_event_open(struct perf_event_attr *hw_event,pid_t pid,int cpu,int group_fd,unsigned long flags)
{
    int ret;
    ret = syscall(__NR_perf_event_open,hw_event,pid,cpu,group_fd,flags);
    return ret;
}

static int fd;

void setup()
{
   struct perf_event_attr pe;
   memset(&pe,sizeof(pe));
   pe.type     = PERF_TYPE_HARDWARE;
   pe.size     = sizeof(pe);
   pe.config   = PERF_COUNT_HW_INSTRUCTIONS;
   pe.disabled = 1;
   pe.exclude_kernel = 1;
   pe.exclude_hv     = 1;
   pid_t pid = 0;
   int cpu   = -1;
   fd = perf_event_open(&pe,-1,0);
   if (fd == -1) {
       fprintf(stderr,"Error opening leader %llx\n",pe.config);
       exit(EXIT_FAILURE);
   }
   ioctl(fd,PERF_EVENT_IOC_RESET,0);
   ioctl(fd,PERF_EVENT_IOC_ENABLE,0);
}

int64_t read()
{
    int64_t count;
    read(fd,&count,sizeof(count));
    return count;
}

std::size_t k;

// The instruction counts do not reflect the cycles consumed here
void inf_loop()
{
    k = 2;
    volatile size_t *p = &k;
    while (*p)
    {
        ++k;
    }
}

int main(int argc,char **argv)
{
   setup();
   thread t1(inf_loop);
   int count = 0;
   for (uint64_t idx = 0; idx < (1ULL << 54); ++idx)
   {
       if (idx % (1ULL << 32) == 0)
       {
           cout << "Cycles: " << read() << endl;
       }
   }
}

解决方法

您想要的是 #include <iostream> #include <type_traits> template <class Derived> class Singleton { public: static Derived& getInstance() { // Assert that the template arg really is derived from the appropriate instantiation of the base class template static_assert(std::is_base_of<Singleton<Derived>,Derived>::value); static Derived s; return s; } virtual void func() { std::cout << "from parent" << std::endl; } }; class Child : public Singleton<Child> { public: void func() override { std::cout << "from child" << std::endl; } }; int main() { auto& s = Child::getInstance(); // s is a Child here s.func(); // Outputs "from child" as expected } 的 perf_event_attr 标志，它将子线程计数合并到父线程中。