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

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Message-ID: <48AB1D62.6030406@keyaccess.nl>
Date:	Tue, 19 Aug 2008 21:22:10 +0200
From:	Rene Herman <rene.herman@...access.nl>
To:	Venki Pallipadi <venkatesh.pallipadi@...el.com>
CC:	Ingo Molnar <mingo@...e.hu>, Dave Airlie <airlied@...il.com>,
	"Li, Shaohua" <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" <dri-users@...ts.sourceforge.net>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	"Siddha, Suresh B" <suresh.b.siddha@...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 21:07, Venki Pallipadi wrote:

> On Tue, Aug 19, 2008 at 07:19:44AM -0700, Rene Herman wrote:

>> 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.
> 
> Hmm. Looks like there are more than 16000 entries in the PAT list!
> 
> This delay may be due to the overhead of parsing this linked list
> everytime for a new entry, rather than any problem with cache setting
> itself.
> 
> I am working on a patch to optimize this pat list parsing for the
> simple case. Should be able to send it out later today, for testing.

Thanks for the reply. It's with 64MB of AGP memory which I guess is at 
the low end these days. Would your reply mean that basically everyone on 
2.6.27 should now be experiencing this?

I noticed it was PAT related due to Shaohua Li's:

http://marc.info/?l=linux-kernel&m=121783222306075&w=2

which lists very different times (patch there did not help any).

As another by the way, probably not surprising but I earlier also tried 
  both unmounting and completely compiling out debugfs just in case I 
was seeing a debugging related sysmptom. No help either.

It's evening here so I'll probably not be able to test until tomorrow.

Rene.
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