Messages in this thread | | | Date | Thu, 21 Aug 2008 07:46:49 +1000 | From | "Dave Airlie" <> | Subject | Re: AGP and PAT (induced?) problem (on AMD family 6) |
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On Thu, Aug 21, 2008 at 7:40 AM, Rene Herman <rene.herman@keyaccess.nl> wrote: > On 20-08-08 21:41, Venki Pallipadi wrote: > >> OK. I have reproduced this list size issue locally and this order 1 >> allocation and set_memory_uc on that allocation is actually coming >> from agp_allocate_memory() -> agp_generic_alloc_page() -> >> map_page_into_agp() agp_allocate_memory breaks higher order page >> requests into order 1 allocs. >> >> On my system I see multiple agp_allocate_memory requests for nrpages 8841, >> 1020, 16, 2160, 2160, 8192. Together they end up resulting in more than 22K >> entries in PAT pages. > > Okay, thanks for the confirmation. > > Now, how to fix... > > Firstly, it seems we can conclude that any expectancy of a short PAT list is > simply destroyed by AGP. I believe the best thing migh be to look into > "fixing" AGP rather than PAT for now? > > In a sense the entire purpose of the AGP GART is collecting non contiguous > pages but given that in practice it's generally still just one or at most a > few regions, going to multi-page allocs sounds most appetising to me. > > All in tree AGP drivers except sgi-agp use agp_generic_alloc_page(), ali via > m1541_alloc_page and i460 via i460_alloc_page.
In the future we will be getting more smaller AGP allocs, so the other problem needs a fix as well.
http://git.kernel.org/?p=linux/kernel/git/airlied/agp-2.6.git;a=shortlog;h=agp-pageattr2
contains some code I started on before that moves the interfaces around, Shaohua has been looking at it as it needs the changes to the set_pages interface as well, which is where I ran out of time/steam last time.
However with alloc/free pages we could change to a higher order allocation function as long as it fell back to lower orders internally.
Dave.
> > Rene. >
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