[Mesa-dev] [PATCH v2 00/37] panfrost: Support batch pipelining

[Boris Brezillon]

On Mon, 16 Sep 2019 16:29:05 -0400
Alyssa Rosenzweig <alyssa at rosenzweig.io> wrote:

> > As a drive-by comment, in case you didn't know, the "standard"
> > solution for avoiding flushing when BO's are written by the CPU (e.g.
> > uniform buffer updates) as documented in ARM's performance guide is to
> > add a copy-on-write mechanism, so that you have "shadow" BO's when the
> > original BO is modified by the user. I believe this is implemented in
> > freedreno, at least there was a talk about it at XDC a few years ago.  
> 
> Yes, this is implemented in freedreno. BO shadowing will be the next
> step once this pipelining code settles down. For now, this series is
> about eliminating the strict flushes between each and every frame of
> each and every FBO that we currently occur now.
> 
> Boris, references on the freedreno model (which is the mesa gold
> standard):
> 
> https://www.x.org/wiki/Events/XDC2016/Program/clark_ooo_rendering.pdf
> https://bloggingthemonkey.blogspot.com/2016/07/dirty-tricks-for-moar-fps.html
> 
> The former presentation is definitely worth a read; evidently we've
> already painted ourselves into some corners :p

I had a quick look at the presentation, and it looks pretty similar to
what is being implemented in this series. The only difference I could
spot is the limitation to 32 batches to avoid usage of sets in the BO
access tracking logic, and that's still something I can change (I'd
prefer to do that in a follow-up patch though).

What specific aspects do you think we got wrong?