1257255 - Add support for listing detached DOM nodes, perhaps by document?

Status: NEW

(DevTools :: Memory, defect, P2)

Description

[Nick Fitzgerald [:fitzgen] [⏰PST; UTC-8]]

With the infrastructure from bug 1056992, we could add a domNodeKind() method to JS::ubi::Node which returns an instance of the following sum type:

  DomNodeKind = NotDomNode
              | AttachedDomNode
              | DetachedDomNode

We could then add a census breakdown that partitions the heap by the DomNodeKind of each node:

  {
    by: "domNodeKind",
    detached: {
      by: "className",
      then: { by: "count", count: true, bytes: true }
    },
    attached: {
      by: "className",
      then: { by: "count", count: true, bytes: true }
    },
    notDomNode: { by: "count", count: true, bytes: true },
  }

This breakdown would yield trees in the "aggregates" view like:

+-------+-------+----------------------+
| Bytes | Count | Group                |
+-------+-------+----------------------+
| BBBBB | CCCCC | - Non-DOM nodes      |
| BBBBB | CCCCC | - Attached DOM nodes |
| BBBBB | CCCCC |   - HTMLDivElement   |
| BBBBB | CCCCC |   - HTMLPElement     |
| BBBBB | CCCCC |   ...                |
| BBBBB | CCCCC | - Detached DOM nodes |
| BBBBB | CCCCC |   - HTMLDivElement   |
| BBBBB | CCCCC |   - HTMLPElement     |
| BBBBB | CCCCC |   ...                |
+-------+-------+----------------------+

When combined with bug 1249788, this would give the following steps for solving/debugging bug 1056992:

  * Take snapshot
  * View "aggregates"
  * Group by "DOM nodes"
  * View all (the only in this case?) detached iframes, and their retaining paths (bug 1249788)
  * Break the detached iframe's retaining path to fix the bug

Additionally, we could also add a census breakdown by document, if that extra level of hierarchy would help.

Comment 1

[Nick Fitzgerald [:fitzgen] [⏰PST; UTC-8]]

Er, those would be the step for solving bug 1256621.