Updates: Cc: jaa...@zoho.com Comment #2 on issue 3172 by laurent.laffont: NewInspector really really slow while parsing XMLNode http://code.google.com/p/pharo/issues/detail?id=3172 From jaayer: Hi Laurent. First, thank you for your screencasts. I am writing to you concerning this issue: http://code.google.com/p/pharo/issues/detail?id=3172&q=xml&colspec=ID%20Type... I only discovered the above last night, as I am not a Pharo core developer and only check the issue tracker occasionally. I am a maintainer of XML-Support, however, so feel free to mail me directly with any issues you have in the future, or at the very least, please post them to the Pharo-Project, Squeak-dev or Moose-dev lists. Now, in your video, which was made back in August, you used version .74 of XML-Parser. If you look at the changelogs of XML-Parser, it is clear that much has changed since that time. It would not be unreasonable to assume that one or more of those changes is responsible for the difficulties you experienced inspecting that XML document. However, if you load version .74, the same version used in your screencast, into a Pharo 1.1 image, the problem is still there (and is in fact much worse), meaning that whatever has changed since August to bring this about, I can say with some confidence that it is not in XML-Parser. Using the latest version of XML-Parser and ignoring the question of causality for a moment, the bottleneck we're observing is in XMLNode>>printOn:. The proof is that disabling XMLNode>>printOn: makes our problem go away. Why then is XML generation suddenly such a bottleneck? The main reason appears to be that the document being inspected is, when printed, roughly 40K in size, and by inspecting it you are causing it to be printed over and over again. I tracked sends of #printOn: and found that inspecting the document and navigating to the "title" element results in #printOn: being sent 300-400 times. The recipients were the document object and the root "feed" element ~350 times. By the time you've navigated to the "feed" element and clicked the "Elements" entry to display its children, #printOn: has already been sent ~150 times. That means the remaining 150-250 sends come when you click on the "title" element or some other child element of the root, and that single additional click results in the generation of roughly 6-10 MBs of XML (150 * 40K to 250 * 40K). *That* is why it's so slow. Now, why does NewInspector cause #printOn: to be sent so much? I honestly don't know. I will forward this to the maintainers of NewInspector to get their input. Maybe NewInspector can be changed to not print inspected objects so often, or to provide them with some way to suppress its printing behavior. It must be pointed out that Pharo also comes with an object explorer that is designed specifically for this usecase of browsing deep object hierarchies. I tried exploring the document with cmd-I (capital i) and encountered no trouble.