Re: AGP and PAT (induced?) problem (on AMD family 6)

From: Rene Herman
Date: Mon Aug 11 2008 - 05:46:40 EST


<ping>

Please note this a 2.6.27 problem (given that PAT isn't enabled by default, not a _pure_ regression I guess, but still).

I also still don't know if you (Andreas), Dave or Yinghai should be the To: on this but given that you've been the only one to react at all...

On 06-08-08 22:57, Rene Herman wrote:

On 06-08-08 15:51, Andreas Herrmann wrote:

On Mon, Aug 04, 2008 at 06:30:32PM +0200, Rene Herman wrote:
What _does_ solve this though is booting with the "nopat" command line parameter. I'm on 2.6.26.1 and have enabled PAT for my AMD Duron myself. With "nopat", there's no problem to be seen anymore -- exiting X specifically is instantaneous.

With or without PAT, my /proc/mtrr is always:

reg00: base=0x00000000 ( 0MB), size= 512MB: write-back, count=1
reg01: base=0x20000000 ( 512MB), size= 256MB: write-back, count=1
reg02: base=0xe8000000 (3712MB), size= 64MB: write-combining, count=1

under X joined by:

reg03: base=0xe4000000 (3648MB), size= 32MB: write-combining, count=2

To get some more debug data, can you please retest with latest kernel
(2.6.27-rc2)

Problem present on vanilla -rc2.

using "debugpat" kernel option and provide dmesg output

No... my kernel message buffer isn't large enough for that :-(

Right, I guess I now know where the delay is coming from. I suppose this is not expected. dmesg as captured after starting X and without "debugpat" at:

http://members.home.nl/rene.herman/pat/dmesg.x

Truncated dmesg with "debugpat":

http://members.home.nl/rene.herman/pat/dmesg.x.debugpat

plus contents of <debugfs>/x86/pat_memtype_list?

Before starting X (1K):

http://members.home.nl/rene.herman/pat/pat_memtype_list.console.debugpat

After starting X (625K):

http://members.home.nl/rene.herman/pat/pat_memtype_list.x.debugpat

(This is with 64MB AGP memory)

More data:

http://members.home.nl/rene.herman/pat/config-2.6.27-rc2-current
http://members.home.nl/rene.herman/pat/xorg.conf
http://members.home.nl/rene.herman/pat/Xorg.0.log
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