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diff --git a/doc/developer-notes.md b/doc/developer-notes.md index a6df17ddd8..40861608a6 100644 --- a/doc/developer-notes.md +++ b/doc/developer-notes.md @@ -17,6 +17,7 @@ Developer Notes - [DEBUG_LOCKORDER](#debug_lockorder) - [Valgrind suppressions file](#valgrind-suppressions-file) - [Compiling for test coverage](#compiling-for-test-coverage) + - [Performance profiling with perf](#performance-profiling-with-perf) - [Locking/mutex usage notes](#lockingmutex-usage-notes) - [Threads](#threads) - [Ignoring IDE/editor files](#ignoring-ideeditor-files) @@ -257,6 +258,51 @@ make cov # A coverage report will now be accessible at `./test_bitcoin.coverage/index.html`. ``` +### Performance profiling with perf + +Profiling is a good way to get a precise idea of where time is being spent in +code. One tool for doing profiling on Linux platforms is called +[`perf`](http://www.brendangregg.com/perf.html), and has been integrated into +the functional test framework. Perf can observe a running process and sample +(at some frequency) where its execution is. + +Perf installation is contingent on which kernel version you're running; see +[this StackExchange +thread](https://askubuntu.com/questions/50145/how-to-install-perf-monitoring-tool) +for specific instructions. + +Certain kernel parameters may need to be set for perf to be able to inspect the +running process' stack. + +```sh +$ sudo sysctl -w kernel.perf_event_paranoid=-1 +$ sudo sysctl -w kernel.kptr_restrict=0 +``` + +Make sure you [understand the security +trade-offs](https://lwn.net/Articles/420403/) of setting these kernel +parameters. + +To profile a running bitcoind process for 60 seconds, you could use an +invocation of `perf record` like this: + +```sh +$ perf record \ + -g --call-graph dwarf --per-thread -F 140 \ + -p `pgrep bitcoind` -- sleep 60 +``` + +You could then analyze the results by running + +```sh +perf report --stdio | c++filt | less +``` + +or using a graphical tool like [Hotspot](https://github.com/KDAB/hotspot). + +See the functional test documentation for how to invoke perf within tests. + + **Sanitizers** Bitcoin Core can be compiled with various "sanitizers" enabled, which add |