Xgl consumes lots of CPU on Gutsy

$ iostat -c 1
Linux 2.6.22-12-generic (pc-thnov-ubuntu) 09/28/2007

avg-cpu: %user %nice %system %iowait %steal %idle
          10.96 0.76 5.32 10.65 0.00 72.30

avg-cpu: %user %nice %system %iowait %steal %idle
          33.67 0.00 17.09 0.00 0.00 49.25

avg-cpu: %user %nice %system %iowait %steal %idle
          35.00 0.00 16.50 0.00 0.00 48.50

avg-cpu: %user %nice %system %iowait %steal %idle
          35.50 0.00 18.00 0.00 0.00 46.50

avg-cpu: %user %nice %system %iowait %steal %idle
          35.00 0.00 18.00 0.00 0.00 47.00

avg-cpu: %user %nice %system %iowait %steal %idle
          35.68 0.00 15.58 0.00 0.00 48.74

avg-cpu: %user %nice %system %iowait %steal %idle
          35.50 0.00 16.50 0.00 0.00 48.00

avg-cpu: %user %nice %system %iowait %steal %idle
          34.50 0.00 16.50 0.00 0.00 49.00

avg-cpu: %user %nice %system %iowait %steal %idle
          34.50 0.00 17.00 0.00 0.00 48.50

avg-cpu: %user %nice %system %iowait %steal %idle
          34.50 0.00 16.50 0.50 0.00 48.50

$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Core(TM)2 CPU T7200 @ 2.00GHz
stepping : 6
cpu MHz : 1000.000
cache size : 4096 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
bogomips : 3994.39
clflush size : 64

processor : 1
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Core(TM)2 CPU T7200 @ 2.00GHz
stepping : 6
cpu MHz : 1000.000
cache size : 4096 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 10
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
bogomips : 3990.03
clflush size : 64

Interesting, for maybe 15 minutes the system was running just as fast as it normally does, then for no apparent reason it got slow again. For the last 3 hours the system has been running with high CPU usage except for those 15 minutes.

I can also hear that my fans are spinning all the time.

Can I stop using Xgl to workaround this problem?

I have now done some investigating. I have found out that this problem arose after I disabled desktop effects. When a while ago switched from disabled to normal in desktop effects, the cpu usage instantly got normal again.

I got other problems with the graphics driver though. I tried to logout and then re-login but then my resolution was totally screwed. Normally I used 1280x1024 at work (docked) and 1680x1050 at home (un-docked). Now I got some 17??x???? resolution. And it was REALLY slow. You could see a window being rendered as if it was a serial console.

I went into screens and graphic and noticed that I was using the vesa driver. Before in Feisty I used fglrx/ATI. I switched to fglrx and rebooted as instructed.

Now the desktop didn't start at all but I got a window telling me I was in a safe mode. I tried switching from all possible resolutions and tried to go back to vesa but I was unable to start my desktop. I stopped gdm, copied my last known working Feisty xorg.conf to the current one and re-started gdm again. Now everything worked good! No high CPU usage either. I'm attaching my Feisty-xorg.conf and my Gutsy-generated xorg.conf.

This doesn't look normal:

$ xrandr
X Error of failed request: BadRequest (invalid request code or no such operation)
  Major opcode of failed request: 151 (RANDR)
  Minor opcode of failed request: 6 ()
  Serial number of failed request: 9
  Current serial number in output stream: 9

Xgl is not meant for running without a compositing manager, thus it is much slower without compiz. (desktop effects) If you dont want to run compiz I would suggest disabeling Xgl alltogether. "touch ~/.config/xserver-xgl/disable"

Ok, but then we have found an issue. The only thing I did was to enable and then disable desktop effects. As a user I sho not be required to manually disabling Xgl.

Thanks for the workaround though :)

You have manually installed xgl-server yourself, right?

This is not an issue any more so I guess it has been fixed. I'm now on Hardy instead of Gutsy.