Flame Graphs for Instruments

Flame graphs are a great way to visualize stack-trace based profiling data. Brendan Gregg’s scripts for generating these graphs accept, among other options, output produced by DTrace. Unfortunately, OS X’s DTrace, when accessed through the command line, contains a bug that prevents it from producing stack traces in most cases. XCode Instruments, on the other hand, is not compromised in this way, but it will not give output similar to dtrace.

What it does provide is an export functionality which generates CSV files containing the exact contents of the details pane, so I wrote a script to do the intermediary work.

http://www.complang.tuwien.ac.at/schani/blog/sgen/instruments-fg.jpg

To produce the CSV file expand all nodes in the call tree (Option-click all the roots) and use the Instrument -> Export Track menu item. Then convert the CSV to the format Brendan’s script understands and feed it with it:

./stackcollapse-instruments.pl out.csv | ./flamegraph.pl >mygraph.svg

flamegraph.png

For an alternative view you can invert the call tree in Instruments and you’ll get a correspondingly inverted flame graph, i.e., the flames go up from callee to caller, as opposed to the other way around when the call tree is not inverted.

About these ads

One thought on “Flame Graphs for Instruments

Comments are closed.