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

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Date:	Tue, 19 Aug 2008 16:19:44 +0200
From:	Rene Herman <rene.herman@...access.nl>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Dave Airlie <airlied@...il.com>, Shaohua Li <shaohua.li@...el.com>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Arjan van de Ven <arjan@...radead.org>,
	dri-users@...ts.sourceforge.net,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: AGP and PAT (induced?) problem (on AMD family 6)

On 19-08-08 12:26, Ingo Molnar wrote:

> * Rene Herman <rene.herman@...access.nl> wrote:
> 
>> On 15-08-08 17:24, Rene Herman wrote:
>>
>>> On 15-08-08 16:22, Ingo Molnar wrote:
>>>
>>>> (more people Cc:-ed)
>>> Thank you. Additional information at http://lkml.org/lkml/2008/8/6/449
>>>
>>>> agreed - +12 seconds wait suggest some rather fundamental breakage.
>>>> Did we go back to uncached for some critical display area that makes
>>>> X start up (shut down) that slowly? Did we mark the BIOS uncacheable
>>>> perhaps, causing X to execute BIOS code very slowly?
>>> Quite a lot "uncached-minus" in those lists. I am desperately trying to 
>>> avoid a clue about mostly anything graphics related so, "I dunno".
>>>
>>> I haven't just disabled PAT yet (although I was about to just do so) 
>>> and am available for testing.
>> <waiting with bated breath>
>>
>> Additional observation with respect to first,next shutdown:
>>
>> With Option "AGPSize" "64", and booted with "nopat", X startup (from 
>> startx<enter> to functional desktop) is approximately 5 seconds, 
>> shutdown is 1 second as calibration times.
>>
>> Booted without "nopat", X startup seems to alternate between 10+ and 
>> 16+ seconds and for shutdown -- the first shutdown after boot takes 
>> some 14 seconds total, subsequent shutdowns settle at around 5 
>> seconds.
> 
> would it be possible to start up and shut down X in the slow case via 
> strace, by doing something like this:
> 
>   strace -f -ttt -TTT -o trace.log startx
> 
> and see which system calls (or other activities) took suspiciously long?

It wouldn't it seems. Root X (needed for the strace) works fine but 
started this way hangs indefinitely.

I believe the 14 seconds for first shutdown to 5 later might be telling. 
Sounds like something might have fixed up uncached entries.

I'd really like a reply from the AGP or PAT side right about now.

Rene.
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