OT: cpu spiking

[Bart Botta]

It sounds like you are running without vsync on one of the drivers,
which means you are displaying frames as fast as you can. "As fast as
you can" usually means either "100% CPU" or "100% GPU" (sometimes
"100% RAM or bus bandwidth").

Check the settings for the driver to see if vsync has been forced to
off, or defaulting to off.

I don't think there is an easy way to control vsync from glut (and
drivers can ignore what programs say anyway), but for a test you can
try something like:

  #+unix
  (let ((p (glut:get-proc-address "glxSwapIntervalEXT")))
    (unless (cffi:null-pointer-p p)
      (cffi:foreign-funcall-pointer p () :int 1 :int))) ;; 0 to
disable vsync, 2 to run at half monitor frame rate, etc

in glut:display-window :before

Note that just checking for a null pointer like that is wrong, and you
should be checking for the presence of the extension first, which
would require some more work with CFFI to get and parse the glx
extension string.

For the case where you aren't drawing anything, I think 100% CPU is
expected. Per freeglut docs, the idle callback is "called continuously
from freeglut while no events are received", which sounds like it
would use 100% CPU. You might try using glut:tick instead (with
:tick-interval argument to window instance creation), as in the
shader-vao example, which runs on a timer instead of constantly.

On Sun, May 29, 2022 at 1:46 PM Orm Finnendahl
<orm.finnendahl at selma.hfmdk-frankfurt.de> wrote:
>
> Hi,
>
>  I might have been a bit unprecise and I just found out it might be
> off topic for this list (see below): This is all related to my laptop
> running an AMD ryzen 7 integrated cpu/gpu on a linux arch system with
> latest sbcl/slime/emacs.
>
> Running (cl-glut-examples:gears) using the open source radeon driver,
> everything works as expected and the REPL reports a framerate of 60
> fps.
>
> Using the closed source pro driver of amd, the framerate goes up to
> ca. 1000 fps and the cpu maxes out. Putting a timer in the display
> function (calling #'glut:post-redisplay), the framerate goes down, but
> the cpu is still above 100%.
>
> I just found out that this is also true for the glxgears program:
> running it with the open source driver give 60 fps, using it with the
> pro driver gives 12000 fps and the cpu maxes out.
>
> Even as this therefore seems to be more realted to the graphics driver
> than cl I'd still appreciate if anyone has an idea, how to deal with
> this...
>
>
> --
> Orm
>
>