[Bug 314928] [NEW] MTRR entry missing since jaunty - is this intentional?

[Sebastian Keller]

Public bug reported:

When comparing /proc/mtrr of intrepid and current jaunty i noticed there
is an entry missing.

Intrepid:
reg00: base=0x00000000 (   0MB), size=1024MB: write-back, count=1
reg01: base=0x40000000 (1024MB), size= 512MB: write-back, count=1
reg02: base=0x5f700000 (1527MB), size=   1MB: uncachable, count=1
reg03: base=0x5f800000 (1528MB), size=   8MB: uncachable, count=1
reg04: base=0xb0000000 (2816MB), size= 256MB: write-combining, count=1

Jaunty:
reg00: base=0x000000000 (    0MB), size= 1024MB, count=1: write-back
reg01: base=0x040000000 ( 1024MB), size=  512MB, count=1: write-back
reg02: base=0x05f700000 ( 1527MB), size=    1MB, count=1: uncachable
reg03: base=0x05f800000 ( 1528MB), size=    8MB, count=1: uncachable

So I tried adding it back by using:
sudo -s
echo "base=0xb0000000 size=0x10000000 type=write-combining" > /proc/mtrr

I have noticed a few things after adding that entry:
- glxgears is now about twice as fast (I know its not a real benchmark ;)
- 2D Performance does not seem affected however (just testing a bit with x11perf/gtkperf)
- it fixes the corruption on the ttys (bug 312677)

I also noticed that this entry gets removed everytime xorg gets
restarted.

But I'm not sure with all the recent changes in memory management if
that entry should still be there or not.

-------------

lspci 
00:00.0 Host bridge: Intel Corporation Mobile 915GM/PM/GMS/910GML Express Processor to DRAM Controller (rev 03)
00:02.0 VGA compatible controller: Intel Corporation Mobile 915GM/GMS/910GML Express Graphics Controller (rev 03)
00:02.1 Display controller: Intel Corporation Mobile 915GM/GMS/910GML Express Graphics Controller (rev 03)
00:1c.0 PCI bridge: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) PCI Express Port 1 (rev 03)
00:1c.2 PCI bridge: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) PCI Express Port 3 (rev 03)
00:1d.0 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #1 (rev 03)
00:1d.1 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #2 (rev 03)
00:1d.2 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #3 (rev 03)
00:1d.3 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB UHCI #4 (rev 03)
00:1d.7 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) USB2 EHCI Controller (rev 03)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev d3)
00:1e.2 Multimedia audio controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) AC'97 Audio Controller (rev 03)
00:1e.3 Modem: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) AC'97 Modem Controller (rev 03)
00:1f.0 ISA bridge: Intel Corporation 82801FBM (ICH6M) LPC Interface Bridge (rev 03)
00:1f.2 IDE interface: Intel Corporation 82801FBM (ICH6M) SATA Controller (rev 03)
00:1f.3 SMBus: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) SMBus Controller (rev 03)
02:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5751M Gigabit Ethernet PCI Express (rev 11)
04:00.0 CardBus bridge: Texas Instruments PCI4510 PC card Cardbus Controller (rev 03)
04:00.1 FireWire (IEEE 1394): Texas Instruments PCI4510 IEEE-1394 Controller (rev 01)
04:02.0 Network controller: Intel Corporation PRO/Wireless 2200BG [Calexico2] Network Connection (rev 05)

** Affects: xserver-xorg-video-intel (Ubuntu)
     Importance: Undecided
         Status: New

-- 
MTRR entry missing since jaunty - is this intentional?
https://bugs.launchpad.net/bugs/314928
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