Full CPU usage on Arch Linux

support
1

I have this code. (I have a folder called include that had glad.h in)

#include <iostream>
#include "include/glad.h"
#include <GLFW/glfw3.h>

int main() {
  glfwInit();

  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
  glfwWindowHint(GLFW_REFRESH_RATE, 60);

  GLFWwindow* window = glfwCreateWindow(800, 800, "Project", NULL, NULL);

  if (window == NULL) {
    std::cout << "Failed to create the GLFW window!" << std::endl;
    glfwTerminate();
    return -1;
  }

  glfwMakeContextCurrent(window);

  glfwSwapInterval(0);

  while(!glfwWindowShouldClose(window)) {
    glfwPollEvents();
  }

  glfwDestroyWindow(window);

  glfwTerminate();

  return 0;
}

If I run it, it causes my CPU to run at 100%

I have tried glfwSwapInterval and glfwWindowHint(GLFW_REFRESH_RATE, 60); as shown in code but neither of them helped, my CPU still runs at 100%.

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2

First of all you should have glfwSwapBuffers(window) inside your while loop. That’s where presenting back buffer will happen.

If you have set glfwSwapInterval to 0 that means do not synchronize with GPU vsync and run your code as much as you can - meaning it will use CPU 100%.

If you want synchronize with GPU vsync then you should have glfwSwapInterval(1); there instead. Then CPU usage should drop down a lot. Because no new frames will be summitted if GPU queue is full.

3

It’s also worth noting that the swap interval is sometimes ignored by drivers due to user settings (and sometimes bugs in drivers).

A technique you can use if you want to only update the visuals on changes in user input is to use glfwWaitEvents or glfwWaitEventsTimeout instead of glfwPollEvents.

However first implement @mmozeiko’s suggestions as these will likely achieve what you need.