Hi On Fri, Jun 21, 2024 at 3:20 AM <dongwon....@intel.com> wrote:
> 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. > Indeed, I don't see much point in doing so, it's pure waste. If you want to benchmark something perhaps. But then, why not simply run a benchmark offscreen? > > 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. > > As it stands now, the option should actually be on the display backend (gtk/gtk-egl), it's not implemented for other backends. I am not convinced this is generally useful to be an extra option though. > 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 > > > -- Marc-André Lureau
