[PATCH] Allocate bo objects to GTT always.

[Michel Dänzer]

On Wed, 2010-02-10 at 12:57 +0200, Pauli Nieminen wrote: 
> 2010/2/10 Michel Dänzer <michel at daenzer.net>:
> > On Tue, 2010-02-09 at 19:31 +0200, Pauli Nieminen wrote:
> >> Memmove/memcpy to vram is very slow operation. To avoid the slow copy
> >> allocate all buffer objects to GTT.
> >
> > I'm not sure that's all there is to it (Have you tried setting it to
> > VRAM instead of GTT?). With write-combining, I wouldn't expect CPU
> > writes to VRAM + blit from VRAM to be significantly slower than CPU
> > writes to GTT + blit from GTT. I think the problem is rather that
> > without specifying a domain explicitly, the BO starts out in system RAM,
> > incurring additional overhead when rendering from it.
> >
> 
> I tested to force bo to vram and it was making the memmove take many
> times more. Video handling is CPU limited because of demanding decode
> process running in CPU while GPU has a lot less to do. So if the move
> over AGP is slow then it is better to ave GPU taking the penalty than
> CPU.

The X driver just copies the decoded YUV data to the BO. So I'm still
not sure where the difference comes from.


> > So while I'm okay with the code change, I suspect the commit log could
> > be better.
> >
> 
> I agree. The commit message is not good enough. I try to rewrite it to
> better explain the change.

Thanks.

> Also minor improvement might be letting ccaller to ask for placement 
> when calling memory allocation. That way only video functions would 
> request GTT placement while for others it could use default.

Hmm, true.


-- 
Earthling Michel Dänzer           |                http://www.vmware.com
Libre software enthusiast         |          Debian, X and DRI developer