# Graphics Streaming Kit (formerly: Vulkan Cereal)

Graphics Streaming Kit (colloquially known as Gfxstream) is a code generator
that makes it easier to serialize and forward graphics API calls from one place
to another:

-   From a virtual machine guest to host for virtualized graphics
-   From one process to another for IPC graphics
-   From one computer to another via network sockets

# Build: Linux

The latest directions for the standalone Linux build are provided
[here](https://crosvm.dev/book/appendix/rutabaga_gfx.html).

# Build: Windows

Make sure the latest CMake is installed. Make sure Visual Studio 2019 is
installed on your system along with all the Clang C++ toolchain components.
Then:

```
mkdir build
cd build
cmake . ../ -A x64 -T ClangCL
```

A solution file should be generated. Then open the solution file in Visual
studio and build the `gfxstream_backend` target.

# Build: Android for host

Be in the Android build system. Then:

```
m libgfxstream_backend
```

It then ends up in `out/host`

This also builds for Android on-device.

# Output artifacts

```
libgfxstream_backend.(dll|so|dylib)
```

# Regenerating Vulkan code

To re-generate both guest and Vulkan code, please run:

scripts/generate-gfxstream-vulkan.sh

# Regenerating GLES/RenderControl code

First, build `build/gfxstream-generic-apigen`. Then run:

```
scripts/generate-apigen-source.sh
```

# Tests

## Windows Tests

There are a bunch of test executables generated. They require `libEGL.dll` and
`libGLESv2.dll` and `vulkan-1.dll` to be available, possibly from your GPU
vendor or ANGLE, in the `%PATH%`.

## Android Host Tests

There are Android mock testa available, runnable on Linux. To build these tests,
run:

```
m GfxstreamEnd2EndTests
```

# Features

## Tracing

The host renderer has optional support for Perfetto tracing which can be enabled
by defining `GFXSTREAM_BUILD_WITH_TRACING` (enabled by default on Android
builds).

The `perfetto` and `traced` tools from Perfetto should be installed. Please see
the [Perfetto Quickstart](https://perfetto.dev/docs/quickstart/linux-tracing) or
follow these short form instructions:

```
cd <your Android repo>/external/perfetto

./tools/install-build-deps

./tools/gn gen --args='is_debug=false' out/linux

./tools/ninja -C out/linux traced perfetto
```

To capture a trace on Linux, start the Perfetto daemon:

```
./out/linux/traced
```

Then, run Gfxstream with
[Cuttlefish](https://source.android.com/docs/devices/cuttlefish):

```
cvd start --gpu_mode=gfxstream_guest_angle_host_swiftshader
```

Next, start a trace capture with:

```
./out/linux/perfetto --txt -c gfxstream_trace.cfg -o gfxstream_trace.perfetto
```

with `gfxstream_trace.cfg` containing the following or similar:

```
buffers {
  size_kb: 4096
}
data_sources {
  config {
    name: "track_event"
    track_event_config {
    }
  }
}
```

Next, end the trace capture with Ctrl + C.

Finally, open https://ui.perfetto.dev/ in your webbrowser and use "Open trace
file" to view the trace.

# Design Notes

## Guest Vulkan

gfxstream vulkan is the most actively developed component. Some key commponents
of the current design include:

-   1:1 threading model - each guest Vulkan encoder thread gets host side
    decoding thread
-   Support for both virtio-gpu, goldish and testing transports.
-   Support for Android, Fuchsia, and Linux guests.
-   Ring Buffer to stream commands, in the style of io_uring.
-   Mesa embedded to provide
    [dispatch](https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/docs/vulkan/dispatch.rst)
    and
    [objects](https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/docs/vulkan/base-objs.rst).
-   Currently, there are a set of Mesa objects and gfxstream objects. For
    example, `struct gfxstream_vk_device` and the gfxstream object
    `goldfish_device` both are internal representations of Vulkan opaque handle
    `VkDevice`. The Mesa object is used first, since Mesa provides dispatch. The
    Mesa object contains a key to the hash table to get a gfxstream internal
    object (for example, `gfxstream_vk_device::internal_object`). Eventually,
    gfxstream objects will be phased out and Mesa objects used exclusively.

# Project Ideas
gfxstream is a first class open source project, and welcomes new contributors.
There are many interesting projects available, for new and experienced software
enthusiasts.  Some ideas include:

1) New OS support (Windows, Haiku, MacOS) support for gfxstream guest
2) Rewriting the gfxstream protocol using python templates and working
   with other FOSS projects to de-duplicate
3) Guided performance optimizations
4) KVM or hypervisor integration to close gap between HW GPU virtualization
5) Improving rutabaga integrations
6) Improving display virtualization

Please reach out to your local gfxstreamist today if you are interested!