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44 lines
1.7 KiB
Markdown
44 lines
1.7 KiB
Markdown
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# Profiling emulator with Valgrind
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Sometimes, it can be helpful to know which parts of your code take most of the CPU time.
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[Callgrind](https://valgrind.org/docs/manual/cl-manual.html) tool from the [Valgrind](https://valgrind.org/)
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instrumentation framework can generate profiling data for a run of Trezor emulator. These can then be visualized
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with [KCachegrind](https://kcachegrind.github.io/).
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Bear in mind that profiling the emulator is of very limited usefulness due to:
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* different CPU architecture,
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* different/mocked drivers,
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* & other differences from actual hardware.
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Still, it might be a way to get *some* insight without a [hardware debugger](../systemview/index.md)
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and a development board.
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Valgrind also currently doesn't understand MicroPython call stack so it won't help you when your code is spending
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a lot of time in pure python functions that don't call out to C. It might be possible to instrument trezor-core
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so that Valgrind is aware of MicroPython stack frames.
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## Build
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```
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make build_unix_frozen TREZOR_EMULATOR_DEBUGGABLE=1 ADDRESS_SANITIZER=0
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```
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With `PYOPT=0`, most of the execution time is spent formatting and writing logs, so it is recommended to use
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`PYOPT=1` (and lose DebugLink) or get rid of logging manually.
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## Run
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If you're using Nix, you can use Valgrind and KCachegrind packages from our `shell.nix`:
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```
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nix-shell --args devTools true --run "poetry shell"
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```
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Record profiling data on some device tests:
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```
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./emu.py -a --debugger --valgrind -c 'sleep 10; pytest ../../tests/device_tests/ -v --other-pytest-args...'
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```
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Open profiling data in KCachegrind (file suffix is different for each emulator process):
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```
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kcachegrind src/callgrind.out.$PID
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```
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