ezyang’s blog

the arc of software bends towards understanding

hp/D3.js: an interactive heap profile viewer

I'm taking a Data Visualization course this fall, and one of our assignments was to create an interactive visualization. So I thought about the problem for a little bit, and realized, “Hey, wouldn’t it be nice if we had a version of hp2ps that was both interactive and accessible from your browser?” (hp2any fulfills this niche partially, but as a GTK application).

A week of hacking later: hp/D3.js, the interactive heap profile viewer for GHC heaps. Upload your hp files, share them with friends! Our hope is that the next time you need to share a heap profile with someone, instead of running hp2ps on it and sending your colleague the ps file, you’ll just upload the hp file here and send a colleague your link. We’ve tested it on recent Firefox and Chrome, it probably will work on any sufficiently modern browser, it definitely won’t work with Internet Explorer.


Some features:

  • You can annotate data points by clicking on the graph and filling in the text box that appears. These annotations are saved and will appear for anyone viewing the graph.
  • You can filter heap elements based on substring match by typing in the “filter” field.
  • You can drill down into more detail by clicking on one of the legend elements. If you click OTHER, it will expand to show you more information about the heap elements in that band. You can then revert your view by pressing the Back button.

Give it a spin, and let me know about any bugs or feature suggestions! (Some known bugs: sometimes Yesod 500s, just refresh until it comes up. Also, we lack backwards animations, axis changing is a little choppy and you can’t save annotations on the OTHER band.)