X using 95% CPU (intel, latest git)

Andy Neitzke neitzke at post.harvard.edu
Thu Aug 13 15:01:34 PDT 2009


I have a Thinkpad X60t, on which I am running the current git master for 
everything related to Xorg, kernel 2.6.31-rc5-00513-ga3620f7, and KDE 4.3 
(with desktop effects turned on).  lspci shows my video as

00:02.0 VGA compatible controller: Intel Corporation Mobile 945GM/GMS, 
943/940GML Express Integrated Graphics Controller (rev 03)

My problem is that frequently, even when the system should be idle, KDE's CPU 
monitor applet shows that one of the two processors is fully loaded.  When 
this happens, "top" blames the X process, showing it using around 95% CPU.  
The problem doesn't happen at the beginning of an X session, but only once I 
have been running for a while.  Once it happens, though, it persists even if I 
close all open applications, kill the window manager and the Plasma desktop, 
and/or stop the compositing manager.  Quitting and restarting the X server 
does fix it.  I haven't found any way to trigger this problem reliably -- I 
have the impression that suspend/resume brings it on faster, but I am not 
totally sure.  I have had this problem for at least a month, perhaps longer.

My question is:  how can I diagnose this problem more precisely?  (Is it 
a symptom of an Xorg bug, or could it that some part of KDE is issuing an 
enormous number of requests to the X server for some reason?)

Thanks for any ideas,

Andy Neitzke

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