Re: AGP and PAT (induced?) problem (on AMD family 6)
From: Venki Pallipadi
Date: Tue Aug 19 2008 - 15:08:16 EST
On Tue, Aug 19, 2008 at 07:19:44AM -0700, Rene Herman wrote:
> On 19-08-08 12:26, Ingo Molnar wrote:
> > * Rene Herman <rene.herman@xxxxxxxxxxxx> 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.
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.
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