Messages in this thread | | | Date | Thu, 21 Aug 2008 07:02:00 +1000 | From | "Dave Airlie" <> | Subject | Re: AGP and PAT (induced?) problem (on AMD family 6) |
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On Wed, Aug 20, 2008 at 8:50 PM, Rene Herman <rene.herman@keyaccess.nl> wrote: > On 20-08-08 12:04, Ingo Molnar wrote: > >> * Venki Pallipadi <venkatesh.pallipadi@intel.com> 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.
I haven't anything to add, I'm the maintainer not the author, all the people who wrote the offending code were already involved.
Dave. > > In the short run and if I'm not just mistaken, the best fix might be to make > PAT dependent on not having a dumb AGP driver (but as said, still looking). > > Note that my chipset is capable of a 2G AGP aperture. That's 512K pages if > fully used, 256K for 1G, 128K for 512M, ... > > Rene. >
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