Revert "wayland: Block for the frame callback in get_back_bo not dri2_swap_buffers"
This reverts commit 25cc8890, though since the code has changed, it was applied manually. The intent of moving blocking from SwapBuffers to get_back_bo, was to avoid unnecessary triple-buffering by ensuring that the compositor had fully processed the previous frame before we started rendering. This means that the only time we would have to resort to triple-buffering would be when the buffer is directly scanned out, thus saving an extra buffer for composition anyway. The 'repaint window' changes introduced in Weston since then, however, have narrowed the window of time between the frame event being sent and the repaint loop needing to conclude, to 7ms by default, in order to reduce latency. This means however that blocking in get_back_bo gives a maximum of 7ms for the entire GL submission to begin and complete. Not only this, but if a client is using buffer_age to avoid full repaints, the buffer-age request will stall in get_back_bo until the frame callback completes, meaning that the client cannot even calculate the repaint area before the 7ms window. The combination of the two meant that WebKit-GTK+ was failing to achieve full framerate on a Minnowboard, due to spending a great deal of its time attempting to query the age of the next buffer before redraw. Revert to the previous behaviour of allowing rendering to begin but delaying SwapBuffers, unless and until we can find a more gentle behaviour. Signed-off-by: Daniel Stone <email@example.com> Reviewed-by: Jonas Ådahl <firstname.lastname@example.org> Reviewed-by: Derek Foreman <email@example.com> Tested-by: Derek Foreman <firstname.lastname@example.org> Cc: Kristian Høgsberg <email@example.com>
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