Confusion about low frame rate with Nvidia GeForge, but hardware rendering seems to work?

Question

All over the years I have always wondered why my Compiz animations on Gnome 2 are not as smooth as on my old Laptop running with Intel GMA 965. Maybe this is related to low frame rates. When I run glxgears (I know, it's no benchmark test) I get only values about 300 frames in 5 seconds:

$ glxgears 
Running synchronized to the vertical refresh.  The framerate should be
approximately the same as the monitor refresh rate.
302 frames in 5.0 seconds = 60.391 FPS
300 frames in 5.0 seconds = 59.919 FPS
300 frames in 5.0 seconds = 59.921 FPS
300 frames in 5.0 seconds = 59.921 FPS
300 frames in 5.0 seconds = 59.921 FPS

The text says that this frame rates are correct, but I can't believe that. This can't be normal, because I found forum entries with frame rates about 20000 or more. I think that my Nvidia GTS 250 can do this much better. Moreover Software Rendering is disabled, so that means that hardware rendering actually works:

$ glxinfo | grep render
direct rendering: Yes
OpenGL renderer string: GeForce GTS 250/PCIe/SSE2
    GL_NV_conditional_render, GL_NV_copy_depth_to_color, GL_NV_copy_image, 
    GL_NV_path_rendering, GL_NV_pixel_data_range, GL_NV_point_sprite, 
    GL_NVX_conditional_render, GL_NVX_gpu_memory_info, GL_OES_depth24, 
    GL_OES_fbo_render_mipmap, GL_OES_get_program_binary, GL_OES_mapbuffer, 

Can anybody explain to me why a frame rate of 300 should be normal or maybe anything else is not correct?

Answer 1

At your output, you can see that it says

Running synchronized to the vertical refresh.  The framerate should be 
approximately the same as the monitor refresh rate.

Since your monitor is presumably running at 60 Hz (as it's the case if it is an LCD, they don't care about refresh rates), this explains what you see, any other frames would be a waste of GPU resources.

To do a real benchmark, you can use games, or something like the Phoronix Test Suite.