Every now and then, X goes into some sort of loop, with the following four
lines being written repeatedly (thousands of times?) to the log:

[184460.635] (II) intel(0): EDID vendor "LEN", prod id 16435
[184460.635] (II) intel(0): Printing DDC gathered Modelines:
[184460.635] (II) intel(0): Modeline "1440x900"x0.0   96.50  1440 1522 1576 1706  900 905 914 943 -hsync -vsync (56.6 kHz eP)
[184460.635] (II) intel(0): Modeline "1440x900"x0.0   80.44  1440 1522 1576 1706  900 905 914 943 -hsync -vsync (47.2 kHz e)

When this happens, CPU usage spikes to ~35% of one core (on a Core 2 Duo, T7300
@ 2.00GHz), and the system responsiveness drops drastically (although it
remains barely usable).

I don't have a clear and precise sense of when it occurs, but it seems to often
happen after resuming from suspend-to-ram. It seems to eventually stop by
itself, with the system returing spontaneously to normal.

Dear Maintainer,

I have a similar problem which might be related to this old issue. I've decided
to reply here because of the similarities I've found between the log files.

I can confirm xorg causes high CPU usage on my E480 Thinkpad laptop.

This started happening after I connected an external monitor via HDMI with a
VGA adapter (as the external monitor does not support HDMI).
High CPU usage loop happens occasionally after dragging a window from the
external monitor to the laptop monitor. This action does not always cause the
loop, but it appears to be one semi-consistent trigger.
It also appears to happen more often after coming back from suspension and
dragging a window between the monitors.

I solve this problem temporarily by killing xorg, which isn't ideal. I would
expect xorg to be able to handle two monitors on my hardware without entering a
high CPU usage loop.

I hope you find this report helpful.