High CPU usage

Game Development
1

Hi,
I have a problem with high CPU usage of my application using SDL+OpenGL. When I run it on Linux mint 9 ( gnome 2 ) it uses only a little CPU, but when I run it on fedora 16 ( gnome 3 ), it uses 100% CPU. I found out that when my app is runing in gnome 3, then gnome-shell uses about 90% of CPU. I tried creating a blank project and there (on fedora) gnome-shell uses about 33% CPU. I don’t have ATI drivers installed on fedora, because they are not yet fully compatible with gnome 3, so I am using mesa3d (I don’t think it may affect it when drawing blank scene).
So my question is what can cause this?
I am not sure if I draw it right way so I will include my code:

#include <SDL/SDL.h>
#include <SDL/SDL_image.h>
#include <SDL/SDL_opengl.h>
#include <GL/gl.h>

void ggDraw( void )
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, 640, 480, 0, -1, 1);

    glFlush();
    SDL_GL_SwapBuffers();
}

int main( int argc, char** argv )
{
    if( SDL_Init( SDL_INIT_VIDEO | SDL_INIT_TIMER ) < 0 )
    {
        printf("could not init SDL\n");
        return -1;
    }
    atexit(SDL_Quit);

    SDL_Surface *screen = NULL;
    screen = SDL_SetVideoMode( 640, 480, 32, SDL_HWSURFACE | SDL_GL_DOUBLEBUFFER | SDL_OPENGL );
    if( screen == NULL )
    {
        printf("could not set video mode\n");
        SDL_Quit();
    }

    Uint8 *keystate = NULL;
    keystate = SDL_GetKeyState( NULL );
    if( keystate == NULL )
    {
        printf("could not get keystate\n");
        SDL_Quit();
    }

	glCullFace( GL_BACK );
	glEnable( GL_CULL_FACE );
	glEnable( GL_TEXTURE_2D );
	glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST );
	glClearColor( 0.0f, 0.0f, 0.0f, 1.0f );
	glShadeModel( GL_SMOOTH );
	glViewport( 0, 0, 640, 480 );

    unsigned char alive = 1;
    long int nowt = 0;
    long int oldt = 0;
    long int time = 0;

    const int FPS = 60;

    while( alive )
    {
        nowt = SDL_GetTicks();

        time = nowt - oldt;
        if( time >= 1000/FPS )
        {
            oldt = nowt;
            SDL_PumpEvents();
            if( keystate[SDLK_ESCAPE] ) alive = 0;
            ggDraw();
        }
        else SDL_Delay(1);
    }

    printf("\nGame ended peacefully.\n");
    SDL_Quit();
    return 0;
}__________

SDL version: 1.2.14

2

Hi,
I have a problem with high CPU usage of my application using SDL+OpenGL. When I run it on Linux mint 9 ( gnome 2 ) it uses only a little CPU, but when I run it on fedora 16 ( gnome 3 ), it uses 100% CPU. I found out that when my app is runing in gnome 3, then gnome-shell uses about 90% of CPU. I tried creating a blank project and there (on fedora) gnome-shell uses about 33% CPU. I don’t have ATI drivers installed on fedora, because they are not yet fully compatible with gnome 3, so I am using mesa3d (I don’t think it may affect it when drawing blank scene).
So my question is what can cause this?

I think the drivers are going to be your issue. Mesa3d is the software rendering version of OpenGL. So when you are using Mesa, the processor has to do all of the graphic processing. When you can use true opengl, then it gets moved to the graphics card. It still seems high to me, but that would be my first guess.

3

[quote:a021409788=“Gekoncze”]Hi,
I have a problem with high CPU usage of my application using SDL+OpenGL. When I run it on Linux mint 9 ( gnome 2 ) it uses only a little CPU, but when I run it on fedora 16 ( gnome 3 ), it uses 100% CPU. I found out that when my app is runing in gnome 3, then gnome-shell uses about 90% of CPU. I tried creating a blank project and there (on fedora) gnome-shell uses about 33% CPU. I don’t have ATI drivers installed on fedora, because they are not yet fully compatible with gnome 3, so I am using mesa3d (I don’t think it may affect it when drawing blank scene).
So my question is what can cause this?

I think the drivers are going to be your issue. Mesa3d is the software rendering version of OpenGL. So when you are using Mesa, the processor has to do all of the graphic processing. When you can use true opengl, then it gets moved to the graphics card. It still seems high to me, but that would be my first guess.[/quote:a021409788]
yes, but when I am drawing blank scene, it uses 33% of CPU… why?

4

I also found out that when I comment out SDL_GL_SwapBuffers(); then the cpu usage of gnome-shell is about 4%. (but of course nothing is then displayed)

5

Here is a look at what i do to ensure that things work at a given rate and that I know how many frames per second I’m getting, cycles per second, and when to update what game data or animation.:
//time tracking td1=time|cycletime|ftime=time since last frame/snapshot
td1=SDL_GetTicks(); timeNow=td1;
cycletime=((float)(td1-td2));
td2=td1;
ftime=ftime+cycletime;

	//stime=how long between snapshots
	sum_frames++;
	//find out if it's snapshot time
	if(ftime>snaptime) {take_snapshot = 1; ftime = 1.666;}
	
	//find out the frames per second 
	if(td1-td3>1000) 
		{
		td3 = td1; display_fps = sum_frames; sum_frames = 0;
		}
6

Give your system some CPU! put a small delay in there to regulate framerate