pps: Documentation

Add documentation for Perfetto and Gfx-pps, together with some perfetto
config files to use as a starting point.

Signed-off-by: Antonio Caggiano <antonio.caggiano@collabora.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>
Acked-by: Emma Anholt <emma@anholt.net>
Reviewed-by: John Bates <jbates@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9652>

docs/index.rst

@@ -71,6 +71,7 @@ and other operating systems.
    osmesa
    debugging
    perf
+   perfetto
    extensions
    application-issues
    viewperf

docs/perfetto.rst

@@ -0,0 +1,110 @@
+Perfetto Tracing
+================
+
+Mesa has experimental support for `Perfetto <https://perfetto.dev>`__ for
+GPU performance monitoring.  Perfetto supports multiple
+`producers <https://perfetto.dev/docs/concepts/service-model>`__ each with
+one or more data-sources.  Perfetto already provides various producers and
+data-sources for things like:
+
+- CPU scheduling events (``linux.ftrace``)
+- CPU frequency scaling (``linux.ftrace``)
+- System calls (``linux.ftrace``)
+- Process memory utilization (``linux.process_stats``)
+
+As well as various domain specific producers.
+
+The mesa perfetto support adds additional producers, to allow for visualizing
+GPU performance (frequency, utilization, performance counters, etc) on the
+same timeline, to better understand and tune/debug system level performance:
+
+- pps-producer: A systemwide daemon that can collect global performance
+  counters.
+- mesa: Per-process producer within mesa to capture render-stage traces
+  on the GPU timeline, track events, etc.
+
+Run
+---
+
+To capture a trace with perfetto you need to take the following steps:
+
+1. Build perfetto from sources available at ``subprojects/perfetto`` following
+   `this guide <https://perfetto.dev/docs/quickstart/linux-tracing>`__.
+
+2. Create a `trace config <https://perfetto.dev/#/trace-config.md>`__, which is
+   a json formatted text file with extension ``.cfg``, or use one of the config
+   files under the ``src/tool/pps/cfg`` directory. More examples of config files
+   can be found in ``subprojects/perfetto/test/configs``.
+
+3. Change directory to ``subprojects/perfetto`` and run a
+   `convenience script <https://perfetto.dev/#/running.md>`__ to start the
+   tracing service:
+
+   .. code-block:: console
+
+      cd subprojects/perfetto
+      CONFIG=<path/to/gpu.cfg> OUT=out/linux_clang_release ./tools/tmux -n
+
+4. Start other producers you may need, e.g. ``pps-producer``.
+
+5. Start ``perfetto`` under the tmux session initiated in step 3.
+
+6. Once tracing has finished, you can detach from tmux with :kbd:`Ctrl+b`,
+   :kbd:`d`, and the convenience script should automatically copy the trace
+   files into ``$HOME/Downloads``.
+
+7. Go to `ui.perfetto.dev <https://ui.perfetto.dev>`__ and upload
+   ``$HOME/Downloads/trace.protobuf`` by clicking on **Open trace file**.
+
+8. Alternatively you can open the trace in `AGI <https://gpuinspector.dev/>`__
+   (which despite the name can be used to view non-android traces).
+
+Troubleshooting
+---------------
+
+Tmux
+~~~~
+
+If the convenience script ``tools/tmux`` keeps copying artifacts to your
+``SSH_TARGET`` without starting the tmux session, make sure you have ``tmux``
+installed in your system.
+
+.. code-block:: console
+
+   apt install tmux
+
+Missing counter names
+~~~~~~~~~~~~~~~~~~~~~
+
+If the trace viewer shows a list of counters with a description like
+``gpu_counter(#)`` instead of their proper names, maybe you had a data loss due
+to the trace buffer being full and wrapped.
+
+In order to prevent this loss of data you can tweak the trace config file in
+two different ways:
+
+- Increase the size of the buffer in use:
+
+  .. code-block:: javascript
+
+      buffers {
+          size_kb: 2048,
+          fill_policy: RING_BUFFER,
+      }
+
+- Periodically flush the trace buffer into the output file:
+
+  .. code-block:: javascript
+
+      write_into_file: true
+      file_write_period_ms: 250
+
+
+- Discard new traces when the buffer fills:
+
+  .. code-block:: javascript
+
+      buffers {
+          size_kb: 2048,
+          fill_policy: DISCARD,
+      }

src/tool/pps/cfg/cpu.cfg

@@ -0,0 +1,20 @@
+buffers {
+  size_kb: 65536
+  fill_policy: RING_BUFFER
+}
+
+data_sources {
+  config {
+    name: "linux.sys_stats"
+    target_buffer: 0
+    sys_stats_config {
+      meminfo_period_ms: 100
+      meminfo_counters: MEMINFO_MEM_AVAILABLE
+
+      stat_period_ms: 100
+      stat_counters: STAT_CPU_TIMES
+    }
+  }
+}
+
+duration_ms: 10000

src/tool/pps/cfg/gpu.cfg

@@ -0,0 +1,29 @@
+buffers {
+  size_kb: 1024
+  fill_policy: RING_BUFFER
+}
+
+data_sources {
+  config {
+    name: "gpu.counters.i915"
+    gpu_counter_config {
+      counter_period_ns: 1000000000
+    }
+    counter_ids: 0
+    counter_ids: 1
+    counter_ids: 2
+    counter_ids: 3
+    counter_ids: 4
+  }
+}
+
+data_sources {
+  config {
+    name: "gpu.counters.panfrost"
+    gpu_counter_config {
+      counter_period_ns: 1000000000
+    }
+  }
+}
+
+duration_ms: 16000