| Message ID | 20240620231727.235841-1-dongwon.kim@intel.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | hw/display/virtio-gpu: Introducing asynchronous guest display render | expand |
Hi On Fri, Jun 21, 2024 at 3:20 AM <dongwon.kim@intel.com> wrote: > From: Dongwon Kim <dongwon.kim@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 > > >
Hi Marc-André, On 7/2/2024 3:29 AM, Marc-André Lureau wrote: > Hi > > On Fri, Jun 21, 2024 at 3:20 AM <dongwon.kim@intel.com > <mailto:dongwon.kim@intel.com>> wrote: > > From: Dongwon Kim <dongwon.kim@intel.com <mailto:dongwon.kim@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? Benchmark score is not the primary reason. The problem we want to avoid is the laggy display update due to too many asynchronous plane updates happening in the guest in certain situations like when moving SW mouse cursor rigorously on the guest. This is because the fence (as well as response for the resource-flush cmd) is signaled in the draw event. > > > 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. We can help to deploy this concept to other backends if needed. > > I am not convinced this is generally useful to be an extra option though. I initially thought this should be the default because the virtio-gpu guest should not be hold by the host for too long in any cases. And this new approach is comparable to the default mode with blob=false where the guest is released as soon as the resource flush is done. Only difference is the resource synchronization using the fence. > > 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
Hi On Tue, Jul 2, 2024 at 10:11 PM Kim, Dongwon <dongwon.kim@intel.com> wrote: > Hi Marc-André, > > On 7/2/2024 3:29 AM, Marc-André Lureau wrote: > > Hi > > > > On Fri, Jun 21, 2024 at 3:20 AM <dongwon.kim@intel.com > > <mailto:dongwon.kim@intel.com>> wrote: > > > > From: Dongwon Kim <dongwon.kim@intel.com <mailto: > dongwon.kim@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? > > Benchmark score is not the primary reason. The problem we want to avoid > is the laggy display update due to too many asynchronous plane updates > happening in the guest in certain situations like when moving SW mouse > cursor rigorously on the guest. This is because the fence (as well as > response for the resource-flush cmd) is signaled in the draw event. > > Presumably, you won't get more frames displayed (perhaps even less due to extra load), so why is it laggy? Is it because the guest is doing too much buffering? Because the mouse event queue isn't being drained between scanouts? > > > > > > 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. > > We can help to deploy this concept to other backends if needed. > Why not make it a gtk display option instead? > > > > I am not convinced this is generally useful to be an extra option though. > > I initially thought this should be the default because the virtio-gpu > guest should not be hold by the host for too long in any cases. And this > new approach is comparable to the default mode with blob=false where the > guest is released as soon as the resource flush is done. Only difference > is the resource synchronization using the fence. > virgl should be blocking rendering too Could you detail your testing setup ? thanks > > > > 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 > >
On 7/2/2024 11:26 PM, Marc-André Lureau wrote: > Hi > > On Tue, Jul 2, 2024 at 10:11 PM Kim, Dongwon <dongwon.kim@intel.com > <mailto:dongwon.kim@intel.com>> wrote: > > Hi Marc-André, > > On 7/2/2024 3:29 AM, Marc-André Lureau wrote: > > Hi > > > > On Fri, Jun 21, 2024 at 3:20 AM <dongwon.kim@intel.com > <mailto:dongwon.kim@intel.com> > > <mailto:dongwon.kim@intel.com <mailto:dongwon.kim@intel.com>>> wrote: > > > > From: Dongwon Kim <dongwon.kim@intel.com > <mailto:dongwon.kim@intel.com> <mailto:dongwon.kim@intel.com > <mailto:dongwon.kim@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? > > Benchmark score is not the primary reason. The problem we want to avoid > is the laggy display update due to too many asynchronous plane updates > happening in the guest in certain situations like when moving SW mouse > cursor rigorously on the guest. This is because the fence (as well as > response for the resource-flush cmd) is signaled in the draw event. > > > Presumably, you won't get more frames displayed (perhaps even less due > to extra load), so why is it laggy? Is it because the guest is doing too > much buffering? Yes, I believe so. Virtio-gpu driver can't issue another resource flush as the previous frame is still on hold by the host. But there are many plane-update requests due to frame buffer updates because of the movement of SW mouse cursor in between. BTW, we currently use dirtyFB update on the guest running Xorg. Maybe using pageflip would make things better but we haven't tried it yet. Because the mouse event queue isn't being drained > between scanouts? > > > > > > > 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. > > We can help to deploy this concept to other backends if needed. > > > Why not make it a gtk display option instead? That is possible but I made it virtio-gpu option as this is specific to virtio-gpu backend. We can consider moving it to gtk layer if it makes more sense. > > > > > > I am not convinced this is generally useful to be an extra option > though. > > I initially thought this should be the default because the virtio-gpu > guest should not be hold by the host for too long in any cases. And > this > new approach is comparable to the default mode with blob=false where > the > guest is released as soon as the resource flush is done. Only > difference > is the resource synchronization using the fence. > > > virgl should be blocking rendering too > > Could you detail your testing setup ? We use ubuntu linux as a guest OS but it's modified for our GFX SRIOV setup. I am not sure if this is the details you are looking for but here is it: we virtualize our GPU using SRIOV. So individual linux guest have their dedicated portion of GPU device that is detected and worked as "render-only" device. And since it is render-only, we pair it with virtio-gpu device/driver that provides display feature. Scanouts on the guest are allocated by virtio-gpu then imported by Mesa driver then used as a main framebuffer. On every plane update done by compositor will get virtio-gpu driver to issue resource-flush (followed by set scanout) to host. Host (QEMU) gets this scanout data as blob (scatter-gather list) then creates its own dmabuf using udmabuf driver. At every resource flush, we block the render pipeline as well as the guest until the rendering if finished for scanout synchronization as you know. We do not use virgl (instead, the normal HW driver for SRIOV-Virtual device is used). So this idea of having render_sync=false is based on 1. glBlitFrameBuffer can be done anytime after resource-flush is received. 2. the guest can be unblocked whenever the blob is used (cloned by glBlitFrameBuffer). > > thanks > > > > > > 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 > > > > -- > Marc-André Lureau
On 7/2/2024 11:26 PM, Marc-André Lureau wrote: > Hi > > On Tue, Jul 2, 2024 at 10:11 PM Kim, Dongwon <dongwon.kim@intel.com > <mailto:dongwon.kim@intel.com>> wrote: > > Hi Marc-André, > > On 7/2/2024 3:29 AM, Marc-André Lureau wrote: > > Hi > > > > On Fri, Jun 21, 2024 at 3:20 AM <dongwon.kim@intel.com > <mailto:dongwon.kim@intel.com> > > <mailto:dongwon.kim@intel.com <mailto:dongwon.kim@intel.com>>> wrote: > > > > From: Dongwon Kim <dongwon.kim@intel.com > <mailto:dongwon.kim@intel.com> <mailto:dongwon.kim@intel.com > <mailto:dongwon.kim@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? > > Benchmark score is not the primary reason. The problem we want to avoid > is the laggy display update due to too many asynchronous plane updates > happening in the guest in certain situations like when moving SW mouse > cursor rigorously on the guest. This is because the fence (as well as > response for the resource-flush cmd) is signaled in the draw event. > > > Presumably, you won't get more frames displayed (perhaps even less due > to extra load), so why is it laggy? Is it because the guest is doing too > much buffering? Yes, I believe so. Virtio-gpu driver can't issue another resource flush as the previous frame is still on hold by the host. But there are many plane-update requests due to frame buffer updates because of the movement of SW mouse cursor in between. BTW, we currently use dirtyFB update on the guest running Xorg. Maybe using pageflip would make things better but we haven't tried it yet. Because the mouse event queue isn't being drained > between scanouts? > > > > > > > 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. > > We can help to deploy this concept to other backends if needed. > > > Why not make it a gtk display option instead? That is possible but I made it virtio-gpu option as this is specific to virtio-gpu backend. We can consider moving it to gtk layer if it makes more sense. > > > > > > I am not convinced this is generally useful to be an extra option > though. > > I initially thought this should be the default because the virtio-gpu > guest should not be hold by the host for too long in any cases. And > this > new approach is comparable to the default mode with blob=false where > the > guest is released as soon as the resource flush is done. Only > difference > is the resource synchronization using the fence. > > > virgl should be blocking rendering too > > Could you detail your testing setup ? We use ubuntu linux as a guest OS but it's modified for our GFX SRIOV setup. I am not sure if this is the details you are looking for but here is it: we virtualize our GPU using SRIOV. So individual linux guest have their dedicated portion of GPU device that is detected and worked as "render-only" device. And since it is render-only, we pair it with virtio-gpu device/driver that provides display function. Scanouts on the guest are allocated by virtio-gpu then imported by Mesa driver then used as a main framebuffer. On every plane update done by compositor will get virtio-gpu driver to issue resource-flush (followed by set scanout) to host. Host (QEMU) gets this scanout data as blob (scatter-gather list) then creates its own dmabuf using udmabuf driver. At every resource flush, we block the render pipeline as well as the guest until the rendering if finished for scanout synchronization as you know. We do not use virgl (instead, the normal HW driver for SRIOV-Virtual device is used). > > thanks > > > > > > 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 > > > > -- > Marc-André Lureau
From: Dongwon Kim <dongwon.kim@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(-)