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

[Rene Herman]

On 20-08-08 12:50, Rene Herman wrote:

> On 20-08-08 12:04, Ingo Molnar wrote:
>
> > * Venki Pallipadi <venkatesh.pallipadi@xxxxxxxxx> wrote:
> >
> > > > 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!
> >
> > hm, btw., why is that?
>
> Because 64M of AGP memory divided by 4K pages is 16K. That is, the 
> underlying problem seems to be AGP drivers using order 0 allocations. 
> I'm looking.
>
> Do note also that this means that Venki's change would not constitite a 
> correct/final fix. Sure, caching the last entry speeds up traversing a 
> 16K entry list but the issue is that there shouldn't be a 16K entry 
> list. Through AGP, or maybe even by coalescing entries in the PAT list 
> if that's at all possible (I guess it's not really).
>
> Even if such a more fundamental fix isn't (easily) available, the PAT 
> code already comments that the list, which is sorted by ->start value, 
> is expected to be short, and should be turned into an rbtree if it isn't 
> which might be slightly less of a bandaid.
>
> Dave Airlie (as the MAINTAINERS entry) can't be arsed to answer email it 
> seems so I've added Dave Jones for a possible comment from the AGP side.
> If I'm reading this right upto now, still many AGP driver (among which 
> my amd-k7-agp) are affected.

This was based on a wrong reading; I was looking at the GATT allocation.

I'm giving up looking until someone can tell me whether or not those 16K 
entries are expected though. I have just one AGP card in a PAT capable 
machine.

How many entries in /debug/x86/pat_memtype_list are there on other AGP 
systems with Option "AGPSize" "64" in their xorg.conf:"Device" section 
(and their AGP aperture set to 64M or bigger in the BIOS)?

Rene.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/