Re: TTM page pool allocator

["Thomas Hellström" <thomas@shipmail.org>]

Dave Airlie skrev:
> On Thu, Jun 25, 2009 at 10:01 PM, Jerome Glisse<glisse@freedesktop.org> wrote:
>   
>> Hi,
>>
>> Thomas i attach a reworked page pool allocator based on Dave works,
>> this one should be ok with ttm cache status tracking. It definitely
>> helps on AGP system, now the bottleneck is in mesa vertex's dma
>> allocation.
>>
>>     
>
> My original version kept a list of wb pages as well, this proved to be
> quite a useful
> optimisation on my test systems when I implemented it, without it I
> was spending ~20%
> of my CPU in getting free pages, granted I always used WB pages on
> PCIE/IGP systems.
>
> Another optimisation I made at the time was around the populate call,
> (not sure if this
> is what still happens):
>
> Allocate a 64K local BO for DMA object.
> Write into the first 5 pages from userspace - get WB pages.
> Bind to GART, swap those 5 pages to WC + flush.
> Then populate the rest with WC pages from the list.
> Granted I think allocating WC in the first place from the pool might
> work just as well since most of the DMA buffers are write only.
>   

Yes, I think in the latter case the user-space driver should take care 
to specify WC from the beginning, when the BO is allocated.

BTW is there any DMA buffer verification taking place on WC buffers on 
Radeon?

> Dave.
>   

/Thomas