From: Dongwon Kim <dongwon....@intel.com> Introducing new virtio-gpu param, 'render_sync' when guest scanout blob is used (blob=true). The new param is used to specify when to start rendering a guest scanout frame.
By default (and so far) rendering of the guest frame is started in the draw event to make sure guest display update is sychronized with host's vsync. But this method inevitably brings some extra wait because most of time, the draw event is not happening right after the guest scanout frame is flushed. This delay often makes the guest stuck at certain frame for too long and causes general performance degradation of graphic workloads on the guest's side especially when the display update rate is high. This unwanted perf drop can be reduced if the guest scanout frame is rendered as soon as it is flushed through 'VIRTIO_GPU_CMD_RESOURCE_FLUSH' msg. The gl display pipeline can be unblocked a lot earlier in this case so that guest can move to the next display frame right away. However, this "asynchrounous" render mode may cause some waste of resources as the guest could produce more frames than what are actually displayed on the host display. This is similar as running rendering apps with no vblank or vsync option. This is why this feature should stay as optional. The param 'render_sync' is set to 'true' by default and this is in line with traditional way while setting it to 'false' is basically enabling this asynchronouse mode. Dongwon Kim (4): hw/display/virtio-gpu: Introducing render_sync param ui/egl-helpers: Consolidates create-sync and create-fence ui/gtk-egl: Start rendering of guest blob scanout if render_sync is off ui/gtk-gl-draw: Start rendering of guest blob scanout if render_sync is off include/hw/virtio/virtio-gpu.h | 3 ++ include/ui/dmabuf.h | 4 +- include/ui/egl-helpers.h | 3 +- hw/display/vhost-user-gpu.c | 3 +- hw/display/virtio-gpu-udmabuf.c | 3 +- hw/display/virtio-gpu.c | 2 + hw/vfio/display.c | 3 +- ui/dbus-listener.c | 2 +- ui/dmabuf.c | 11 +++- ui/egl-helpers.c | 27 ++++------ ui/gtk-egl.c | 93 ++++++++++++++++++--------------- ui/gtk-gl-area.c | 90 +++++++++++++++++++------------ 12 files changed, 146 insertions(+), 98 deletions(-) -- 2.34.1