From 8d39ce7bce249f9f6bd87ba175cf4b215f83defe Mon Sep 17 00:00:00 2001 From: "Eric R. Smith" Date: Fri, 21 Nov 2025 11:28:50 -0400 Subject: [PATCH] panfrost: add benchmarking documentation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add some notes on getting reproducible benchmark numbers on panfrost/panthor based SoCs. Reviewed-by: Alejandro Piñeiro Reviewed-by: Iago Toral Quiroga Part-of: --- docs/drivers/panfrost/benchmarking.rst | 71 ++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) create mode 100644 docs/drivers/panfrost/benchmarking.rst diff --git a/docs/drivers/panfrost/benchmarking.rst b/docs/drivers/panfrost/benchmarking.rst new file mode 100644 index 00000000000..2b084c748f7 --- /dev/null +++ b/docs/drivers/panfrost/benchmarking.rst @@ -0,0 +1,71 @@ +Benchmarking Panfrost +===================== + +Obtaining reproducible benchmark timings can sometimes be tricky on Mali +based SoCs. There are a number of things that can be done to make the timings +more predictable. + +Make sure the device is actively cooled (to eliminate thermal throttling) +------------------------------------------------------------------------- + +This isn't strictly speaking necessary, if you use low enough frequencies +in the steps below, but it is recommended. + +Fix the GPU frequency +--------------------- + +If power management is allowed to vary the GPU frequency, this will lead to +uncertainty in benchmark figures, particularly for shorter benchmark runs. + +On most systems, the GPU frequency can be set to a fixed value via a command +like the following (run it as root, sudo alone won't allow the redirection): + +.. code-block:: sh + + cat /sys/devices/platform/fb000000.gpu/devfreq/fb000000.gpu/min_freq > /sys/devices/platform/fb000000.gpu/devfreq/fb000000.gpu/max_freq + +This forces the GPU to always use its minimum frequency. You could reverse +`min_freq` and `max_freq` to fix it to its maximum frequency, if your system +is adequately cooled. + +Fix the CPU frequency +--------------------- + +It is easy to overlook the role the CPU plays in driver performance. To set +its frequency to a fixed value, install the `linux-cpupower` package and +run something like: + +.. code-block:: sh + + sudo cpupower frequency-info + sudo cpupower frequency-set -d 1.20 + sudo cpupower frequency-set -u 1.20 + sudo cpupower frequency-info + +Adjust the numbers based on what the board actually supports (seen in +the first `frequency-info`. It is best to choose fairly low settings +unless you're confident of the board's cooling. + +Pin the benchmark program to a particular core +---------------------------------------------- + +This is especially important on devices with a big.LITTLE architecture, where +having the benchmark be scheduled on a different kind of core can drastically +change the performance. But even without this, variations in cache residency +and scheduling of kernel tasks can lead to changes in benchmark timing. + +Experience shows that using a little core for the benchmark program +tends to give more reproducible results (probably because they have smaller +caches, and also are less likely to be scheduled to by the kernel). +However, forcing the benchmark to run on a little core could change the +bottleneck from GPU to CPU, so watch out for that. + +Pinning a task to a particular core is done with the `taskset` command. An +example for the Rock5b (rk3588) board is: + +.. code-block:: sh + + taskset 0x04 glmark2-es2-wayland + +Replace `0x04` with an appropriate mask for your board, and +`glmark2-es2-wayland` with the benchmark program to be used.