Perfetto Tracing¶

Mesa has experimental support for Perfetto for GPU performance monitoring. Perfetto supports multiple producers 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 on the CPU timeline, etc.

The exact supported features vary per driver:

Supported data-sources¶
Driver	PPS Counters	Render Stages
Freedreno	`gpu.counters.msm`	`gpu.renderstages.msm`
Turnip	`gpu.counters.msm`	`gpu.renderstages.msm`
Intel	`gpu.counters.i915`	`gpu.renderstages.intel`
Panfrost	`gpu.counters.panfrost`
PanVK	`gpu.counters.panfrost`	`gpu.renderstages.panfrost`
V3D	`gpu.counters.v3d`
V3DV	`gpu.counters.v3d`

Run¶

To capture a trace with Perfetto you need to take the following steps:

Build Mesa with perfetto enabled.

# Configure Mesa with perfetto
mesa $ meson . build -Dperfetto=true -Dvulkan-drivers=intel,broadcom -Dgallium-drivers=
# Build mesa
mesa $ meson compile -C build

Build Perfetto from sources available at subprojects/perfetto.

# Within the Mesa repo, build perfetto
mesa $ cd subprojects/perfetto
perfetto $ ./tools/install-build-deps
perfetto $ ./tools/gn gen --args='is_debug=false' out/linux
perfetto $ ./tools/ninja -C out/linux

# Example arm64 cross compile instead
perfetto $ ./tools/install-build-deps --linux-arm
perfetto $ ./tools/gn gen --args='is_debug=false target_cpu="arm64"' out/linux-arm64

More build options can be found in this guide.

Select a trace config, likely src/tool/pps/cfg/system.cfg which does whole-system including GPU profiling for any supported GPUs). Other configs are available in that directory for CPU-only or GPU-only tracing, and more examples of config files can be found in subprojects/perfetto/test/configs.
Start the PPS producer to capture GPU performance counters.

mesa $ sudo meson devenv -C build pps-producer

Start your application (and any other GPU-using system components) you want to trace using the perfetto-enabled Mesa build.

mesa $ meson devenv -C build vkcube

Capture a perfetto trace using tracebox.

mesa $ sudo ./subprojects/perfetto/out/linux/tracebox --system-sockets --txt -c src/tool/pps/cfg/system.cfg -o vkcube.trace

Go to ui.perfetto.dev and upload vkcube.trace by clicking on Open trace file.
Alternatively you can open the trace in AGI (which despite the name can be used to view non-android traces).

CPU Tracing¶

Mesa’s CPU tracepoints (MESA_TRACE_*) use Perfetto track events when Perfetto is enabled. They use mesa.default and mesa.slow categories.

Currently, only EGL and the following drivers have CPU tracepoints.

Freedreno
Panfrost
Turnip
V3D
VC4
V3DV

Render stage data sources¶

The render stage data sources are the driver-specific traces of command buffer execution on the GPU.

The Vulkan API gives the application control over recording of command buffers as well as when they are submitted to the hardware, and command buffers can be recorded once and reused repeatedly. Trace commands are normally only recorded into a command buffer when a perfetto trace is active. Most applications don’t reuse command buffers, so you’ll see traces appear shortly after the trace was started, but if you have one of the rare applications that reuses command buffers, you’ll need to set the MESA_GPU_TRACES environment variable before starting a Vulkan application :

MESA_GPU_TRACES=perfetto ./build/my_vulkan_app

Driver Specifics¶

Below is driver specific information/instructions for the PPS producer.

Freedreno / Turnip¶

The Freedreno PPS driver needs root access to read system-wide performance counters, so you can simply run it with sudo:

sudo ./build/src/tool/pps/pps-producer

Intel¶

The Intel PPS driver needs root access to read system-wide RenderBasic performance counters, so you can simply run it with sudo:

sudo ./build/src/tool/pps/pps-producer

Another option to enable access wide data without root permissions would be running the following:

sudo sysctl dev.i915.perf_stream_paranoid=0

Alternatively using the CAP_PERFMON permission on the binary should work too.

A particular metric set can also be selected to capture a different set of HW counters :

INTEL_PERFETTO_METRIC_SET=RasterizerAndPixelBackend ./build/src/tool/pps/pps-producer

Vulkan applications can also be instrumented to be Perfetto producers. To enable this for given application, set the environment variable as follow :

PERFETTO_TRACE=1 my_vulkan_app

Panfrost¶

The Panfrost PPS driver uses unstable ioctls that behave correctly on kernel version 5.4.23+ and 5.5.7+.

To run the producer, follow these two simple steps:

Enable Panfrost unstable ioctls via kernel parameter:
```
modprobe panfrost unstable_ioctls=1
```
Alternatively you could add panfrost.unstable_ioctls=1 to your kernel command line, or echo 1 > /sys/module/panfrost/parameters/unstable_ioctls.
Run the producer:
```
./build/pps-producer
```

V3D / V3DV¶

As we can only have one performance monitor active at a given time, we can only monitor 32 performance counters. There is a need to define the performance counters of interest for pps_producer using the environment variable V3D_DS_COUNTER.

V3D_DS_COUNTER=cycle-count,CLE-bin-thread-active-cycles,CLE-render-thread-active-cycles,QPU-total-uniform-cache-hit ./src/tool/pps/pps-producer

Troubleshooting¶

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:

buffers {
    size_kb: 2048,
    fill_policy: RING_BUFFER,
}

Periodically flush the trace buffer into the output file:
```
write_into_file: true
file_write_period_ms: 250
```

Discard new traces when the buffer fills:

buffers {
    size_kb: 2048,
    fill_policy: DISCARD,
}