X11 performance regressions

[Knut Petersen <Knut_Petersen@t-online.de>]

I compared the performance of X11 on two otherwise idle machines.

Hardware
========
Both have
identical mainboards (Aopen i915GMm-hfs),
identical memory and BIOS setup.
Both cpus are Intel Pentium M mobile (Dothan).
One runs at 1.86 Mhz, the other runs at 2.00 MHz

Software
=======
1.86 MHz system:
opensuse 11.2
X.Org X Server 1.6.5
Release Date: 2009-10-11
kernel 2.6.38.5

2.00 MHz system:
opensuse 11.4
X.Org X Server 1.10.99
git-tree, 2011-may-7
kernel 2.6.39-rc4-drm-intel-staging

x11perf results
===========

The first line always gives the test result of the 2.00 Mhz system with the current Xorg,
the second line gives the test result of the 1.86 MHz sytem with Xorg 1.6.5. Read a
few representative examples:

10000000 trep @   0.0032 msec (309000.0/sec): Dot
40000000 trep @   0.0006 msec (1650000.0/sec): Dot

  45000 trep @   0.5973 msec (  1670.0/sec): 500x500 rectangle
 100000 trep @   0.4282 msec (  2340.0/sec): 500x500 rectangle

2000000 reps @   0.0034 msec (296000.0/sec): 1x1 stippled rectangle (8x8 stipple)
8000000 reps @   0.0007 msec (1420000.0/sec): 1x1 stippled rectangle (8x8 stipple)

   1500 trep @  22.4602 msec (    44.5/sec): 500x500 stippled rectangle (8x8 stipple)
   3000 trep @   9.2680 msec (   108.0/sec): 500x500 stippled rectangle (8x8 stipple)

 100000 trep @   0.4043 msec (  2470.0/sec): Fill 10x10 trapezoid
1000000 trep @   0.0336 msec ( 29700.0/sec): Fill 10x10 trapezoid

The old X on the PC with the slower cpu is always significantly faster than the current git code,
very often more than 5 times as fast, and a number of test show 1.6.5 to be more than 12 times
faster than 1.10.99.

I did not use any special configuration options at compile time
1.10.99 was built using the following commands.

export PREFIX=/home/knut/local
export PKG_CONFIG_PATH=$PREFIX/lib/pkgconfig
export PATH=$PREFIX/bin:$PATH
export ACLOCAL="aclocal -I $PREFIX/share/aclocal"
export LD_LIBRARY_PATH=$PREFIX/lib
export PYTHONPATH=$PREFIX/lib/python2.7/site-packages
util/modular/build.sh -g $PREFIX

Could anybody please explain why the old server is so much faster?
Are there any compile time or runtime options that could/should be used?

cu,
 Knut