由于使用事件而产生的开销

我有一个自定义的线程池类,它创建了一些线程,每个线程都等待自己的事件(信号)。将新作业添加到线程池时,它会唤醒第一个空闲线程,以便执行该作业。

问题如下:我有大约1000个循环,每个循环大约10000次迭代。这些循环必须按顺序执行,但我有4个CPU可用。我试图做的是将10000个迭代循环拆分为42000个迭代循环,即每个线程一个循环。但我必须等待4个小循环完成,然后才能进入下一个“大”迭代。这意味着我不能捆绑工作。

我在Windows上,因此我使用 CreateEvent() 然后使用 WaitForMultipleObjects(2, handles, false, INFINITE) 直到主线程调用 SetEvent() .

我的问题是:使用事件花费“很多”时间是否正常?如果是这样的话,我是否可以使用另一种机制来节省时间?

下面是一些要说明的代码(从我的线程池类复制的一些相关部分):

// thread function
unsigned __stdcall ThreadPool::threadFunction(void* params) {
    // some housekeeping
    HANDLE signals[2];
    signals[0] = waitSignal;
    signals[1] = endSignal;

    do {
        // wait for one of the signals
        waitResult = WaitForMultipleObjects(2, signals, false, INFINITE);

        // try to get the next job parameters;
        if (tp->getNextJob(threadId, data)) {
            // execute job
            void* output = jobFunc(data.params);

            // tell thread pool that we're done and collect output
            tp->collectOutput(data.ID, output);
        }

        tp->threadDone(threadId);
    }
    while (waitResult - WAIT_OBJECT_0 == 0);

    // if we reach this point, endSignal was sent, so we are done !

    return 0;
}

// create all threads
for (int i = 0; i < nbThreads; ++i) {
    threadData data;
    unsigned int threadId = 0;
    char eventName[20];

    sprintf_s(eventName, 20, "WaitSignal_%d", i);

    data.handle = (HANDLE) _beginthreadex(NULL, 0, ThreadPool::threadFunction,
        this, CREATE_SUSPENDED, &threadId);
    data.threadId = threadId;
    data.busy = false;
    data.waitSignal = CreateEvent(NULL, true, false, eventName);

    this->threads[threadId] = data;

    // start thread
    ResumeThread(data.handle);
}

// add job
void ThreadPool::addJob(int jobId, void* params) {
    // housekeeping
    EnterCriticalSection(&(this->mutex));

    // first, insert parameters in the list
    this->jobs.push_back(job);

    // then, find the first free thread and wake it
    for (it = this->threads.begin(); it != this->threads.end(); ++it) {
        thread = (threadData) it->second;

        if (!thread.busy) {
            this->threads[thread.threadId].busy = true;

            ++(this->nbActiveThreads);

            // wake thread such that it gets the next params and runs them
            SetEvent(thread.waitSignal);
            break;
        }
    }

    LeaveCriticalSection(&(this->mutex));
}