[Mesa-dev] [PATCH 2/7] vbo: Add a predraw resolve callback

[Chad Versace]

On Sat 12 Sep 2015, Chris Wilson wrote:
> On Thu, Sep 10, 2015 at 08:41:37AM +0100, Chris Wilson wrote:
> > http://people.freedesktop.org/~ickle/vbo/
> > 
> > ministat 63c4b7e_bench_synmark:OglBatch7 2fbce8b_bench_synmark:OglBatch7
> > x 63c4b7e_bench_synmark:OglBatch7
> > + 2fbce8b_bench_synmark:OglBatch7
> > +------------------------------------------------------------------------------+
> > |                                                    x               +         |
> > |                                                    x               +         |
> > |                                                    x   x           + +  +    |
> > |                                                    x   x           +++ +++   |
> > |                                               x  x x   x x         +++ +++   |
> > |                                               x  xxx  xx xx        +++++++   |
> > |                                              xx xxxxx xxxxx    +  ++++++++++ |
> > |x                          x              x   xxxx**xx xxxxxx  x++ +++++++++++|
> > |                                          |________AM________|   |____A____|  |
> > +------------------------------------------------------------------------------+
> >     N           Min           Max        Median           Avg        Stddev
> > x  50       8.96925       10.4881       10.2213     10.203639    0.22548474
> > +  50         10.16       10.8186       10.6612     10.649134    0.12242131
> > Difference at 95.0% confidence
> > 	0.445495 +/- 0.0719896
> > 	4.36604% +/- 0.705529%
> > 	(Student's t, pooled s = 0.181425)
> > 
> > Looking at the total number of intel_update_state() vs brw_draw_prims()
> > for OglBatch7 doesn't alone explain the change as there are nearly the
> > same number of calls to both. (Though we do see similar changes in the
> > INTEL_NO_HW versions of OglBatch0 and OglBatch7, but that data is much
> > more noisy.)
> 
> The explanation for the improvement in the OglBatch7 case seems to lie
> in the removal of the mutex dance from intel_update_state() and the
> reduction of the post-resolve _mesa_update_state() recursions.
> -Chris

I agree with the patch series' big idea: depth and hiz resolves should
most definitely be triggered by draws, not by state updates. And that's
how it used to work before brw_meta arrived, back when blorp ruled the
resolves.

However, this patch series is scary :) I'm poring over it today.