Description of problem:
gnome-terminal seems to make the xorg process use 100% of the CPU for a
2-3 seconds when scrolling text such as dmesg. Does not happen with
xterm.
Fixed when using Option ShadowFB in xorg.conf, although this is obviously
non-ideal. Also causes general system slowdown in X applications, but to a
lesser degree.

Version-Release number of selected component (if applicable):
xorg-x11-server-Xorg-1.2.0-6.fc7

How reproducible:
On this machine, always.

Steps to Reproduce:
1. Install rawhide
2. Open gnome-terminal, type dmesg
3. Watch the CPU usage hit 100% for a couple of seconds on a dual core 1.6GHz
machine.
  
Actual results:
LOTS of CPU usage, 2 or three seconds.

Expected results:
A few ms of 0.X% CPU usage.

Additional info:

hughsie@localhost:~$ opreport -cl --demangle=smart `which Xorg`
warning: /usr/bin/Xorg could not be read.
CPU: Core Solo / Duo, speed 1662.68 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Unhalted clock cycles) with a unit mask of 0x00
(Unhalted core cycles) count 860000
samples  %        image name               symbol name
-------------------------------------------------------------------------------
1582     88.2812  libfb.so                 fbCompositeSolidMask_nx8888x8888Cmmx
  1582     100.000  libfb.so                
fbCompositeSolidMask_nx8888x8888Cmmx [self]
-------------------------------------------------------------------------------
136       7.5893  libfb.so                 fbCompositeSrcAdd_8888x8888mmx
  136      100.000  libfb.so                 fbCompositeSrcAdd_8888x8888mmx [self]
-------------------------------------------------------------------------------
65        3.6272  nv_drv.so                NVSync
  65       100.000  nv_drv.so                NVSync [self]
-------------------------------------------------------------------------------
5         0.2790  Xorg                     (no symbols)
  5        100.000  Xorg                     (no symbols) [self]
-------------------------------------------------------------------------------
2         0.1116  libfb.so                 fbPolySegment32
  2        100.000  libfb.so                 fbPolySegment32 [self]
-------------------------------------------------------------------------------
1         0.0558  libc-2.5.90.so           free
  1        100.000  libc-2.5.90.so           free [self]
-------------------------------------------------------------------------------
1         0.0558  libfb.so                 fbSolidFillmmx
  1        100.000  libfb.so                 fbSolidFillmmx [self]
-------------------------------------------------------------------------------