Pierre-Eric Pelloux-Prayer
09dc0fb2ee
For DRI_PRIME setup where the dGPU -> iGPU copy can happen asynchronously,
we need to ensure that we're not continuously reusing the same back buffer.
The existing code relies on XCB_PRESENT_EVENT_IDLE_NOTIFY to decide if
a buffer is busy or idle. If this event is received before the hardware
is done using the buffer, then it will reuse the same buffer and introduce
a dependency between the copy and the next frame.
This commit mitigates this by trying to allocate a different back buffer
when called from dri3_get_buffer (not from dri3_find_back_alloc, because it
seems that it expects dri3_get_buffer - see 0cc4c7e33e).
An alternative would be to query the busy-ness using is_resource_busy
but this complicates the code to achieve the same result.
One affected app is Unigine Superposition, and this change improves the
score by 0% - 5% depending on the settings.
This behavior is enabled if PIPE_CAP_PREFER_BACK_BUFFER_REUSE is 0.
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Acked-by: Michel Dänzer <mdaenzer@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12788>
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