[Mesa-dev] Linux Graphics Next: Userspace submission update

Christian König ckoenig.leichtzumerken at gmail.com
Tue Jun 1 10:21:56 UTC 2021

Am 01.06.21 um 11:02 schrieb Michel Dänzer:
> On 2021-05-27 11:51 p.m., Marek Olšák wrote:
>> 3) Compositors (and other privileged processes, and display flipping) can't trust imported/exported fences. They need a timeout recovery mechanism from the beginning, and the following are some possible solutions to timeouts:
>> a) use a CPU wait with a small absolute timeout, and display the previous content on timeout
>> b) use a GPU wait with a small absolute timeout, and conditional rendering will choose between the latest content (if signalled) and previous content (if timed out)
>> The result would be that the desktop can run close to 60 fps even if an app runs at 1 fps.
> FWIW, this is working with
> https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880 , even with implicit sync (on current Intel GPUs; amdgpu/radeonsi would need to provide the same dma-buf poll semantics as other drivers and high priority GFX contexts via EGL_IMG_context_priority which can preempt lower priority ones).

Yeah, that is really nice to have.

One question is if you wait on the CPU or the GPU for the new surface to 
become available? The former is a bit bad for latency and power management.

Another question is if that is sufficient as security for the display 
server or if we need further handling down the road? I mean essentially 
we are moving the reliability problem into the display server.


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