Possible Performance Regression with Mesa

[Lucas Stach]

Am Donnerstag, dem 25.04.2024 um 07:56 -0300 schrieb Joao Paulo Silva
Goncalves:
> 
> 
> On Thu, Apr 25, 2024 at 5:58 AM Lucas Stach <l.stach at pengutronix.de> wrote:
> 
> > Etnaviv added some resource tracking to fix issues with a number of
> > use-cases, which did add some CPU overhead and might cost some
> > performance, but should no be as dramatic as the numbers you are seeing
> > here.
> 
> Good to know. Thanks!
> 
> > Since the glmark2 cumulative score can be skewed quite heavily by
> >  single tests, it would be interesting to compare the results from
> >  individual benchmark tests. Do you see any outliers there or is the
> >  performance drop across the board?
> 
> It seems to have a perfomance impact on overall the individual benchmarks too, for example:

I can reproduce the issue, but sadly there is no simple fix for this,
as it's a bad interaction between some of the new features.
At the core of the issue is the dmabuf-feedback support with the chain
of events being as follows:

1. weston switches to the scanout tranche, as it would like to put the
surface on a plane
2. the client reallocates as linear but does so on the render node
3. weston still isn't able to put the buffer on the plane, as it's
still scanout incompatible due to being non-contig, so needs to fall
back to rendering
4. now we are stuck at a linear buffer being used for rendering, which
is very non-optimal

I'll look into improving this, but can make no commitments as to when
I'll be able to get around to this.

Regards,
Lucas