RE: AGP PAT issue.

From: Pallipadi, Venkatesh
Date: Mon Oct 13 2008 - 13:16:56 EST




>-----Original Message-----
>From: Thomas Hellstrom [mailto:thomas@xxxxxxxxxxxxxxxxxxxx]
>Sent: Thursday, October 09, 2008 8:53 AM
>To: Rene Herman
>Cc: Pallipadi, Venkatesh; Ingo Molnar; Dave Airlie; Li,
>Shaohua; Yinghai Lu; Andreas Herrmann; Arjan van de Ven; Linux
>Kernel; Siddha, Suresh B; Thomas Gleixner; H. Peter Anvin;
>Dave Jones; Alan Hourihane
>Subject: Re: AGP PAT issue.
>
>Rene Herman wrote:
>> On 13-09-08 02:26, Pallipadi, Venkatesh wrote:
>>
>>>>>> Haven't been subcribed to any lists recently and someone was
>>>>>> talking about "the other thread" before but just noticed that
>>>>>> an-rc6 was cut.
>>>>>>
>>>>>> Please note that the shutdown issue remains unfixed in it (I'm
>>>>>> doing my coalescing changes locally).
>>>>>>
>>>>> here's what is pending in tip/x86/pat for v2.6.28:
>>>>>
>>>> Only talking about .27 and just making sure again the
>issue is known.
>>>>
>>>> The above mentioned subject for the entry cache one ("fix Xorg
>>>> startup/shutdown slowdown with PAT") after all mistakingly says it
>>>> does something for shutdown.
>>>>
>>> Can you try the patch here
>>> http://www.ussg.iu.edu/hypermail/linux/kernel/0809.1/2074.html
>>>
>>> That should resolve both reserve and free issues..
>>
>> Not for .27 though.
>>
>> Rene.
>
>Hi!
>What's the status on this?

This patch is now in upstream git and well on its way to .28

>There are graphics devices we're working with that require large
>(non-AGP) write-combined memory buffers at any time.
>We can solve the tlb- and cache flush latencies by using pools of these
>pages to allocate from and free to, but sooner or later we'll probably
>end up with _huge_ memtype lists. In the (very unlikely) worst case I
>guess they'd contain every other lowmem page in they system.
>
>If I understand things correctly the patch above will fix this issue?
>Will it be considered for future kernel inclusion.

Yes this patch will help the above case.

Thanks,
Venki
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