Re: TTM vs GEM discussion questions

[Jerome G. <gl...@fr...>]

On Fri, 16 May 2008 12:20:29 +0200
Thomas Hellström <th...@tu...> wrote:
> Cache coherency and caching policy is a non-issue with user-space VRAM 
> mappings.
> I think with the pwrite approach you will run into severe performance 
> problems if used for
> long-lived buffers.
> 
> Think EXA, vertical lines, perhaps no tiling.

If i feel the need to map vram then i will do it. What i am stating
is that i find painfull to map object in vma (tlb flush) and to have
to deal with limited vram access (how should i handle such things ?
split the vram into one mappable the other not ? then what to do
when one object might fit in ram only if a part of it is mappable
while another not ?) So to sumup i find object mapping in vma
painfull and cumberstone, i am well aware that in the software
rendering case this was the fastest path but i am expecting that
current hw and future hw will be able to support all rendering
primitive we use.

So in the end what i like in GEM is freedom on that kind of
choice, no complexe fencing, and the code size which enable
you to understand most of it in 5min of code reading while
for TTM despite numerous question i ask and hour i spend
starring at the code i still fill unconfortable with the
code and i have hard time to figure out by which path goes
most of my use.

Cheers,
Jerome Glisse <gl...@fr...>