Possible Performance Regression with Mesa

[Daniel Stone]

On Thu, 25 Apr 2024 at 13:08, Lucas Stach <l.stach at pengutronix.de> wrote:
> 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

Oh man, sorry about that, that shouldn't happen. As long as
drmModeAddFB2 is failing, we should be marking the buffer as
non-importable, and then hinting the client back towards tiled.

That being said, yeah, having the client render to linear and skip
composition is definitely going to be better!

Cheers,
Daniel