[Mesa-dev] [PATCH 57/70] i965: Stage blitted buffer uploads through the common upload bo

[Chris Wilson]

On Mon, Aug 10, 2015 at 10:40:29AM +0200, Daniel Vetter wrote:
> On Fri, Aug 07, 2015 at 09:14:01PM +0100, Chris Wilson wrote:
> > Reuse the common upload bo for the temporary blitter storage to try and
> > minimise resource usage.
> > 
> > Caveats: this may impose a read-read relationship on the buffer between
> > the blitter and render engines, and may add stalls on old kernels.
> 
> Note that read-read has only landed in 4.2, hence we might want to hold
> off on this one a bit until most distros have upgraded to this ;-)

It's not that big of a penalty. Mesa has already closed and submitted the
render batch due to the change of engines and will be forced to do a
sync anyway because it is writing into a busy object (busy presumably
due to a render operation). You've already lost.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre