commit f634499044059e863173858793c717aa0634c1ae Author: Pierre-Antoine Rault par@rigelk.eu Date: Fri Jan 13 17:01:49 2017 +0100
improved doc/HelpfulTools.md on profiling Tor
(Based on join work at https://pad.riseup.net/p/profiling-tor) --- doc/HACKING/HelpfulTools.md | 55 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+)
diff --git a/doc/HACKING/HelpfulTools.md b/doc/HACKING/HelpfulTools.md index a7f36e6..8e9051d 100644 --- a/doc/HACKING/HelpfulTools.md +++ b/doc/HACKING/HelpfulTools.md @@ -142,6 +142,12 @@ run `make test-network`. We also have scripts to run integration tests using Stem. To try them, set `STEM_SOURCE_DIR` to your Stem source directory, and run `test-stem`.
+Profiling Tor +------------- + +Ongoing notes about Tor profiling can be found at +https://pad.riseup.net/p/profiling-tor + Profiling Tor with oprofile ---------------------------
@@ -167,6 +173,55 @@ Here are some basic instructions * `opcontrol --dump;` * `opreport -l that_dir/*` - Profit + +Profiling Tor with perf +----------------------- + +This works with a running Tor, and requires root. + +1. Decide how long you want to profile for. Start with (say) 30 seconds. If that + works, try again with longer times. + +2. Find the PID of your running tor process. + +3. Run `perf record --call-graph dwarf -p <PID> sleep <SECONDS>` + + (You may need to do this as root.) + + You might need to add `-e cpu-clock` as an option to the perf record line + above, if you are on an older CPU without access to hardware profiling + events, or in a VM, or something. + +4. Now you have a perf.data file. Have a look at it with `perf report + --no-children --sort symbol,dso` or `perf report --no-children --sort + symbol,dso --stdio --header`. How does it look? + +5a. Once you have a nice big perf.data file, you can compress it, encrypt it, + and send it to your favorite Tor developers. + +5b. Or maybe you'd rather not send a nice big perf.data file. Who knows what's + in that!? It's kinda scary. To generate a less scary file, you can use `perf + report -g > <FILENAME>.out`. Then you can compress that and put it somewhere + public. + +Profiling Tor with gperftools aka Google-performance-tools +---------------------------------------------------------- + +This should work on nearly any unixy system. It doesn't seem to be compatible +with RunAsDaemon though. + +Beforehand, install google-perftools. + +1. You need to rebuild Tor, hack the linking steps to add `-lprofiler` to the + libs. You can do this by adding `LIBS=-lprofiler` when you call `./configure`. + +Now you can run Tor with profiling enabled, and use the pprof utility to look at +performance! See the gperftools manual for more info, but basically: + +2. Run `env CPUPROFILE=/tmp/profile src/or/tor -f <path/torrc>`. The profile file + is not written to until Tor finishes execuction. + +3. Run `pprof src/or/tor /tm/profile` to start the REPL.
Generating and analyzing a callgraph ------------------------------------