Re: Intel graphics CPU usage - SDVO detect bogosity?

Markus Trippelsdorf
2010-08-16T02:51:54Z

On Sun, Aug 15, 2010 at 07:32:15PM -0700, Linus Torvalds wrote:
> I started wondering why 'top' was showing an otherwise idle system as
> having a load average of 0.5+, and worker threads constantly using the
> CPU.
>
> So I did a system-wide profile, and got the attached output (look at
> it in a really wide terminal).
>
> There seems to be something _seriously_ wrong with i915 SDVO detect.
> This is on an Apple Mac Mini (hey, your favorite problem child!), and
> apparently it spends 20% of its non-idle CPU time just doing udelay's
> for the i2c SDVO connection detection.
>
> That sounds a bit wrong, doesn't it?
>
> I don't know how recent this is - it might have been going on for some
> time without me noticing. It's the wife's computer, and the same thing
> doesn't seem to happen on my Core i5 desktop
>
> Any ideas? Any information I can give about the machine?

You're not alone. I'm seeing similar things on my machine (AMD,Radeon).
The monitor outputs are polled every 10 sec in drivers/gpu/drm/drm_crtc_helper.c.

There is a patch attached to the following bug report that disables
polling and solves the problem for me:
http://bugs.freedesktop.org/show_bug.cgi?id=29536

--
»A man who doesn't know he is in prison can never escape.«
William S. Burroughs