glClear：RAM使用量略有增加

Question

以下是我的小opengl程序，只是绘制一个三角形。有一个小故障，当我添加glClear（）函数时，RAM每秒略微增加大约10K。为什么会这样？

int screenwidth=537, screenheight=716;
GLFWwindow* window;

if (!glfwInit()) return -1;

window = glfwCreateWindow(screenwidth, screenheight, "Test", NULL, NULL);
if(!window){glfwTerminate(); return -1;}

glfwMakeContextCurrent(window);

//Setting up the OpenGL Context
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, screenwidth, screenheight, 0, 0, 1);
glDisable(GL_DEPTH_TEST);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glClearColor(1,0.9176f,0.1259f,1);

//The rendering loop
while (!glfwWindowShouldClose(window)){

    glClear(GL_COLOR_BUFFER_BIT);

    glColor3f(1.0f, 1.0f, 1.0f);
    glBegin(GL_TRIANGLES);
    glVertex2f(0, 0);
    glVertex2f(.5f, .5f);
    glVertex2f(0, .5f);
    glEnd();

    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS){
        glfwSetWindowShouldClose(window, GL_TRUE);
    }

    glfwSwapBuffers(window);
    glfwPollEvents();
}

示例：https://www.youtube.com/watch?v=MOxyaxuTsyI