简单的C++ SFML程序高CPU使用率

我目前正在开发平台并尝试实现时间步长,但对于超过60的帧速率限制,CPU使用率从1%上升到25%甚至更高.

我制作了这个最小程序来演示这个问题.代码中有两条注释(第10-13行,第26-30行)描述了问题以及我测试过的内容.

请注意,FPS的东西与问题无关(我认为).

我试着让代码简洁明了:

#include 
#include 
#include 
#include 

int main() {
  // Window
  std::shared_ptr window;
  window = std::make_shared(sf::VideoMode(640, 480, 32), "Test", sf::Style::Close);
  /*
  When I use the setFramerateLimit() function below, the CPU usage is only 1% instead of 25%+
  (And only if I set the limit to 60 or less. For example 120 increases CPU usage to 25%+ again.)
  */
  //window->setFramerateLimit(60);

  // FPS text
  sf::Font font;
  font.loadFromFile("font.ttf");
  sf::Text fpsText("", font, 30);
  fpsText.setColor(sf::Color(0, 0, 0));

  // FPS
  float fps;
  sf::Clock fpsTimer;
  sf::Time fpsElapsedTime;
  /*
  When I set framerateLimit to 60 (or anything less than 60) 
  instead of 120, CPU usage goes down to 1%.
  When the limit is greater, in this case 120, CPU usage is 25%+
  */
  unsigned int framerateLimit = 120;
  sf::Time fpsStep = sf::milliseconds(1000 / framerateLimit);
  sf::Time fpsSleep;
  fpsTimer.restart();

  while (window->isOpen()) {
    // Update timer
    fpsElapsedTime = fpsTimer.restart();
    fps = 1000.0f / fpsElapsedTime.asMilliseconds();

    // Update FPS text
    std::stringstream ss;
    ss << "FPS: " << std::fixed << std::setprecision(0) << fps;
    fpsText.setString(ss.str());

    // Get events
    sf::Event evt;
    while (window->pollEvent(evt)) {
      switch (evt.type) {
      case sf::Event::Closed:
        window->close();
        break;
      default:
        break;
      }
    }

    // Draw
    window->clear(sf::Color(255, 255, 255));
    window->draw(fpsText);
    window->display();

    // Sleep
    fpsSleep = fpsStep - fpsTimer.getElapsedTime();
    if (fpsSleep.asMilliseconds() > 0) {
      sf::sleep(fpsSleep);
    }

  }

  return 0;
}

我不想使用SFML的setFramerateLimit(),而是我自己的睡眠实现,因为我将使用fps数据来更新我的物理和东西.

我的代码中是否存在逻辑错误？我没有看到它,因为它的帧速率限制为例如60(或更低).是因为我有60赫兹的显示器吗？

PS:使用SFML的窗口 - > setVerticalSync()不会改变结果