Question

我有两个进程A和B应该使用Windows 10上的Boost.Interprocess通过共享内存快速交换数据。我的问题：notify_all()和wait()之间的时间似乎很慢（定期15毫秒）。我结束了编写一个简单的应用程序来使用Windows下的QueryPerformanceCounter来重现此问题，以获得准确的计时。 PerformanceCounter的init内部放在共享内存中，以便比较A和B之间的时间。

我使用这个放在共享内存中的常见结构：

namespace bi = boost::interprocess;
struct SharedStruct
{
    double          time; // Time to share between process A and B

    // Sync objects
    bi::interprocess_mutex      mutex;
    bi::interprocess_condition  cond_data_ready;
    volatile bool               data_ready;
    volatile bool               exited;

    // timing information for debug
    long long       counter_start;
    double          pc_freq;
};

第一个进程创建共享内存，初始化时序信息，然后运行此函数：

// Process A (producer)
void Run()
{
    for (int i = 0; i != 10; ++i)
    {
        Sleep(1000); // Sleep 1 sec to simulate acquiring data
        // In my real code, this is not a Sleep but a WaitForMultipleObjects() call
        double counter;
        {
            bi::scoped_lock<mutex_type> lock(m_main_struct->mutex);
            double counter = GetCounter();
            m_main_struct->time = counter;
            m_main_struct->data_ready = true;
        }
        m_main_struct->cond_data_ready.notify_all();
    }
    bi::scoped_lock<mutex_type> lock(m_main_struct->mutex);
    m_main_struct->exited = true;
    m_main_struct->cond_data_ready.notify_all();
}

进程B打开已存在的共享内存并读取数据。

// Process B : read and print timestamps diff
void Run()
{
    bi::scoped_lock<mutex_type> lock(m_main_struct->mutex);
    while (!m_main_struct->exited)
    {
        m_main_struct->cond_data_ready.wait(lock);
        if(m_main_struct->data_ready)
        {
            m_main_struct->data_ready = false;
            double counter = GetCounter();
            double diff = counter - m_main_struct->time;
            std::cout << boost::lexical_cast<std::string>(counter) << " and the diff is : " << diff << std::endl;
        }
    }
    std::cout << "Exiting..." << std::endl;
}

输出类似于：

3011.8175661852633 and the diff is : 0.0160456
4044.836078038385 and the diff is : 15.6379
5061.9643649653617 and the diff is : 15.5186
6079.200594853236 and the diff is : 15.6448
7075.2902152258657 and the diff is : 0.0218803
8119.8910797177004 and the diff is : 26.4905
9099.8308285825678 and the diff is : 0.0379259
10122.977664923899 and the diff is : 0.0393846
11140.647854688354 and the diff is : 0.0145869
12158.33992478272 and the diff is : 0.0237037
Exiting...

有时，notify_all()和wait()之间的时间小于1毫秒（这很好），但有时大约是15毫秒，这是我认为的太多了。如果我使用Windows事件通知/等待，则此问题消失（约0.05毫秒）。

这是正常的吗？有什么想法吗？

Boost.Interprocess notify（）性能

0 个答案: