OpenGL empty project uses too much CPU - c++

Question

I have created a simple OpenGL program, following the LearnOpenGL tutorial. It just creates a window and fills it with a color. I am using Visual Studio 2019.
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow* window);
int main() {
// Initialize GLFW
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
// Create GLFW Window
GLFWwindow* window = glfwCreateWindow(800, 600, "Golden Retriever", NULL, NULL);
if (window == NULL) {
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
// Initialize GLAD
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// Render Loop
while (!glfwWindowShouldClose(window)) {
processInput(window);
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 0;
}
void framebuffer_size_callback(GLFWwindow* window, int width, int height) {
glViewport(0, 0, width, height);
}
void processInput(GLFWwindow* window) {
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
The program works perfectly, however it uses way too much CPU (around 50%). Is it something in Visual Studio properties, or am i just doing something wrong in my code?

Answer 1

You can enable vsync with glfwSwapInterval(1)

Answer 2

The way Windows measures CPU time falls flat on its face for processes that spend most of their time blocking (=waiting) on kernel calls. What happens in your case is, that in order to V-Sync your program has to wait for the vertical retrace to happen. That usually involves waiting for a synchronization object that's locked from kernel context.d
In order to make Windows measure consumed CPU time accurately add a Sleep(1) right before the buffer swap call.