[Speed Test] Why is MPMCQueue significantly faster than ProducerConsumerQueue? about folly

[Zheng-Bicheng]

My coding is as follow:

folly::ProducerConsumerQueue<int> BufferProducerConsumerQueue(1000);
void ProducerConsumerQueueProducer() {
    for (int i = 0; i < DATA_NUM; ++i) {
        while (!BufferProducerConsumerQueue.write(i));
    }
}
void ProducerConsumerQueueConsumer() {
    int value;
    for (int i = 0; i < DATA_NUM; ++i) {
        while (!BufferProducerConsumerQueue.read(value));
    }
}
static void TestProducerConsumerQueue(benchmark::State &state){
    for (auto _ : state) {
        std::thread producerThread(ProducerConsumerQueueProducer);  // 创建生产者线程
        std::thread consumerThread(ProducerConsumerQueueConsumer);  // 创建消费者线程
        producerThread.join();  // 等待生产者线程结束
        consumerThread.join();  // 等待消费者线程结束
    }
}
BENCHMARK(TestProducerConsumerQueue)->UseRealTime()->Unit(benchmark::kSecond);

folly::MPMCQueue<int> BufferMPMCQueue(1000);
void MPMCQueueProducer() {
    for (int i = 0; i < DATA_NUM; ++i) {
        while (!BufferMPMCQueue.write(i));
    }
}
void MPMCQueueConsumer() {
    int value;
    for (int i = 0; i < DATA_NUM; ++i) {
        while (!BufferMPMCQueue.read(value));
    }
}
static void TestMPMCQueue(benchmark::State &state){
    for (auto _ : state) {
        std::thread producerThread(MPMCQueueProducer);  // 创建生产者线程
        std::thread consumerThread(MPMCQueueConsumer);  // 创建消费者线程
        producerThread.join();  // 等待生产者线程结束
        consumerThread.join();  // 等待消费者线程结束
    }
}
BENCHMARK(TestMPMCQueue)->UseRealTime()->Unit(benchmark::kSecond);

And the speed results is:

------------------------------------------------------------------------------
Benchmark                                    Time             CPU   Iterations
------------------------------------------------------------------------------
TestProducerConsumerQueue/real_time       8.46 s         0.000 s             1
TestMPMCQueue/real_time                   5.47 s         0.000 s             1