docs: Add documentation for gpuvis.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22505>

docs/gpu-perf-tracing.rst

@@ -8,3 +8,4 @@ TODO: Add general tips for performance measurement.
 
    u_trace
    perfetto
+   gpuvis

docs/gpuvis.rst

@@ -0,0 +1,67 @@
+Gpuvis Tracing Annotations
+==========================
+
+`Gpuvis <https://github.com/mikesart/gpuvis>`__ is a tool to visualize ftrace
+traces, with support for most GPU drivers to show GPU activity.
+
+Mesa can emit trace markers to be displayed in Gpuvis, which is useful for
+figuring out why e.g. stalls are happening.
+
+Run on Linux
+------------
+
+Any traces can be made with trace-cmd. The Gpuvis repository contains
+`scripts <https://github.com/mikesart/gpuvis/tree/master/sample>`__ for
+configuring the markers needed for GPU events. To start tracing:
+
+.. code-block:: console
+
+   sh trace-cmd-setup.sh && sh trace-cmd-start-tracing.sh
+   # Start your game etc. Then to capture a trace
+   sh trace-cmd-capture.sh
+   # and to finally stop
+   sh trace-cmd-stop-tracing.sh
+
+The resulting trace file can be opened with Gpuvis.
+
+Run on Steamos
+--------------
+
+Steamos includes a script (`gpu-trace <https://github.com/lostgoat/gpu-trace>`__)
+to capture traces.
+
+.. code-block:: console
+
+   sudo gpu-trace
+   # Press Ctrl+C to stop capture and open report in gpuvis
+
+Note that on Steamos gpuvis is actually not installed by default, but the
+script does write a gpu-trace.zip file in the current working directory. To
+open it you'll want to do the following on your development machine:
+
+.. code-block:: console
+
+   scp sd-host:gpu-trace.zip ./
+   unzip gpu-trace.zip
+   ./trace-cmd convert -i *.dat -o converted.dat --compression none --file-version 6
+   gpuvis *.json converted.dat
+
+The main advantage of the gpu-trace script is that it has an integration with
+perf, so Gpuvis can also visualize perf samples in the timeline. Note that the
+perf file is preprocessed before being put into the zip file, so the trace is
+portable between machines.
+
+
+Annotations in Steam games
+--------------------------
+
+Steam games are run in a container, and need the environment variable
+PRESSURE_VESSEL_DEVEL=1 to set up the tracing filesystem so the trace marker
+can be written. This can e.g. be done by going to the game properties in
+Steam and setting the command line to
+
+.. code-block:: console
+
+   PRESSURE_VESSEL_DEVEL=1 %command%
+
+Then you can run the game as usual, and the driver will write trace annotations.