Re: [Mesa3d-dev] Gallium software fallback/draw command failure

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

On Mon, Mar 01, 2010 at 03:24:51PM +0100, Olivier Galibert wrote:
> On Mon, Mar 01, 2010 at 02:57:08PM +0100, Jerome Glisse wrote:
> > validate function i have in mind as virtualy a zero cost (it will
> > boil down to a bunch of add followed by a test) and what validate
> > would do would be done by draw operation anyway.
> 
> Not "would", "will".  You have no way to be sure nothing changed
> between validate and draw, unless you're happy with an interface that
> will always be unusable for multithreading.  So you'll do it twice for
> something that will always tell "yes" except once in a blue moon.
> 
> And if you want to be sure that validate passes implies draw will
> work, it's often more than a bunch of adds.  Allocations can fail even
> if the apparent free space is enough.  See "fragmentation" and
> "alignment", among others.
> 
> Morality: reduce the number of operations in the normal (often called
> fast) path *first*, ask questions later.  Trying to predict failures
> is both unreliable and costly.  Xorg/mesa is perceived slow enough as
> it is.
> 
>   OG.
> 

Do you have solution/proposal/idea on how to handle the situation
i am describing ?

Cheers,
Jerome