This is a collection of quick and dirty experiments in parsing heap dumps provided by Chrome Dev Tools when you hit 'Save' on a heap dump.
The goals here are:
- Handle massive heap dumps (>2GB) such as those you can get from badly behaving webapps like an overloaded riot/web.
- Provide cheap & cheerful programmatic access to basic heap statistics in order to see what number & what type of objects are present - particularly as the pie charts and summaries from Chrome Dev Tools itself don't always seem to add up correctly.
Originally this was a simple wrapper around the heapsnapshot npm
package, albeit using JSONStream to load the massive JSON heap files
without running into node's string size limits (~1GB on 64-bit;
~250MB on 32-bit). Unfortunately this still runs out of heap, perhaps
due to heapsnapshot itself not being designed for massive heaps.
So instead there's a perl script called heap-analyser.pl which naively
parses a snapshots and prints out common aggregate stats instead. It doesn't
currently parse edge data, so can't be used to model the retainers or
dominators graph for the heap.
The end result is less ambiguous pie charts:
...and stuff like this:
The node app could probably be made to work by making JSONStream emit the
nodes, edges & strings elements more incrementally rather than trying to emit
a single JSON structure in one fell swoop - unless heapsnapshot then ends up
being the bottleneck.