我們的系統後臺處理模仿memcached，採用libevent的事件通知實現資料的傳送，採用linux的條件變數實現業務接收處理。因其存在可替換性，故對這兩種方式的效率進行了部分測試。下面貼上部分原始碼：

預測: 因條件變數機制是linux底層做的，而libevent的事件通知則是通過執行緒接收與事件關聯，再通過管道實現資料傳遞。故應該是條件變數更快一點。

1，測試程式碼，傳送資料並寫管道通知或者寫條件變數通知：

static void* test1(void* args)
{
	int i = 1;
	char buff[1] = {'m'};
	for (; i < 100000001; ++i)
	{
		pthread_mutex_lock(&mutexQueue);
		q1.push(i);
		pthread_mutex_unlock(&mutexQueue);
		//如採用寫管道，就不採用broadcast，如採用broadcast，就不採用寫管道
		if (write(threads->notify_send_fd, buff, 1) != 1)
		{
			LOG_ERROR("Write Pipe Failed!");
		}
		//pthread_cond_broadcast(&gCondReadInner);
	}
}
 

2，libevent事件與管道建立

{
		threads = static_cast<LIBEVENT_THREAD*>(calloc(1, sizeof(LIBEVENT_THREAD)));
		threads->base = event_base_new();
		int fds[2] = {-1, -1};
		if (pipe(fds))
		{
			LOG_ERROR("Create Pipe Failed!");
			return FAILED;
		}
		threads->notify_receive_fd = fds[0];
		threads->notify_send_fd = fds[1];

		//建立事件
		threads->notify_event = event_new(threads->base, threads->notify_receive_fd,EV_READ | EV_PERSIST, pipefunc, threads);
		if (NULL == threads->notify_event)
		{
			LOG_ERROR("Create Notify Event Failed!");
			return FAILED;
		}

		//新增事件
		if (-1 == event_add((event*)threads->notify_event, 0))
		{
			LOG_ERROR("Add Notify Event Failed!");
			return FAILED;
		}


		//準備結束，啟動迴圈執行緒
		int iRet = 0;
		if ((iRet = pthread_create(&threads->thread_id, NULL, CLinkMgr::WorkerLibevent, (void*)threads)) != 0)
		{
			LOG_ERROR("Create Thread Failed! -- %d", iRet);
			return FAILED;
		}
	}
 

3，具體的管道接收執行緒實現

<pre name="code" class="cpp">static void pipefunc(int fd, short which, void* arg)
{
	char buff[1] = {0};
	if (read(fd, buff, 1) != 1)
	{
		LOG_ERROR("Read Text Failed!");
		return;
	}
	static int count = 0;
	int x;
	pthread_mutex_lock(&mutexQueue);
	x = q1.front();
	q1.pop();
	pthread_mutex_unlock(&mutexQueue);
	count++;
	if (count == 1)
	{
		LOG_ERROR("++++++++++++++++++++++ Count Start");
	}
	else if (count >= 100000000)
	{
		LOG_ERROR("++++++++++++++++++++++ Count End!, count = %d", count);
	}

}
 

4，具體的條件變數讀資料實現

static void* ReadWait(void* args)
{
	//設定執行緒對cancel狀態的反應，允許退出執行緒
	(void)pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
	//設定執行緒對cancel的執行時機，立即執行
	(void)pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, NULL);

	static int count = 0;
	while (1)
	{
		pthread_mutex_lock(&mutexQueue);
		while (q1.empty())
		{
			pthread_cond_wait(&gCondReadInner, &mutexQueue);
		}
		
		int x = q1.front();
		q1.pop();
		pthread_mutex_unlock(&mutexQueue);
		if (x == 1)
		{
			LOG_ERROR("++++++++++++++++++++++ Count Start");
		}
		else if (x >= 100000000)
		{
			LOG_ERROR("++++++++++++++++++++++ Count End!, count = %d", x);
		}
	}
}

	//測試執行緒
	pthread_t tid;
	(void)pthread_create(&tid, NULL, test1, NULL);
	
	/*
	//建立wait執行緒讀
	pthread_t tid1;
	(void)pthread_create(&tid1, NULL, ReadWait, NULL);
	
		//測試執行緒
	pthread_t tid;
	(void)pthread_create(&tid, NULL, test1, NULL);
	*/
	
	//迴圈處理
	(void)event_base_dispatch(base);

測試結果

綜上，條件變數的執行緒間通訊效率是libevent寫管道事件通知的3倍，符合我們的預測條件！！！。

也許這就是為什麼memcached僅採用libevent寫管道進行接收，而傳送呼叫系統的傳送函式的原因吧。