Hi Pekka, On 12 October 2017 at 07:56, Pekka Paalanen <[email protected]> wrote: > On Wed, 11 Oct 2017 09:01:30 -0500 > Matt Hoosier <[email protected]> wrote: >> I'll have a look there. One thing that for simplicity I left out of >> the original description above is that this custom Weston output has a >> fast-path very similar to the normal DRM scanout optimizations. So if >> that path gets hit, it's often the live DRM buffer supplied by the >> client whose dmabuf fd we're using in the background processing. I'm >> not sure that I can robustly assume that the clients support stacking >> up arbitrarily deep numbers of renderbuffers. If all the buffers >> getting chewed on were owned strictly inside the compositor, I think >> that relying on 4-deep buffering in Mesa might be do-able. I'll have >> to think about whether that makes sense to generalize to client >> buffers as well. > > It has always been the intention that yes, also clients do need to > allocate more buffers as they need. But, reality probably disagrees, > since there has not been too much of actual need to use more than three > buffers, so toolkit writers might assume there is a low limit to how > many buffers there might ever be necessary. It is definitely worth to > test though, and I would not preclude filing bugs against toolkits to > raise their limits. > > I would be a little surprised if EGL GBM and Wayland platforms as > implemented in Mesa would differ in their limits though, but that > should be easy to fix.
If you look at dri2_egl_surface::color_buffers inside src/egl/drivers/dri2/egl_dri2.h, you can see that it's 4 for both platforms, and has been since 2013, when eglSwapInterval(0) became a thing. There's some rationale, but it's essentially: one that you're rendering into, one you've attached to the compositor, one the compositor's attached to the kernel, and one that the compositor hasn't yet released. I can't speak for non-Mesa sources. Cheers, Daniel _______________________________________________ wayland-devel mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/wayland-devel
