1411116 - Slim down children replies from server using diffs

Status: NEW

(DevTools :: Inspector, enhancement, P2)

Description

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

As noticed by :jdescottes in bug 1366693, when a page dynamically adds child nodes asynchronously, the inspector slow downs tremendously.

Specifically, if keep growing a parent by 1 node, the client will send n requests for the server to list all children, which in turn means sum(1 .. n) node actor forms are created.

With 300 nodes:

- 300 children requests
- 45,150 node forms

We might see a little batching and avoid this maximum, but still it can be quite a lot.

Time to load test page[1]:

- inspector closed: 1.7s
- inspector open: 3 - 4.8s

We should be able to reduce the work involved and data transferred by only sending add / removed child info, as opposed to a full set of children each time.

[1]: https://bug1366693.bmoattachments.org/attachment.cgi?id=8917000

Comment 1

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

Retesting after bug 1171482 landed:

- inspector closed: 1.7s
- inspector open: 4.8 - 5.5s

Inspector open is now a bit slower, which seems suspicious.  I'll ask in that bug.

Comment 2

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

Okay, seems like my tests were bad or something.  Updated results:

+--------------------+--------------------+-------------------+
|                    |  Inspector Closed  |   Inspector Open  |
+--------------------+--------------------+-------------------+
| Revert throttle    |        1.7s        |   9.78 - 11.95s   |
| 100ms throttle     |        1.7s        |   4.76 - 5.49s    |
| 100ms w/ form memo |        1.7s        |   1.83 - 1.89s    |
| 500ms throttle     |        1.7s        |   2.0  - 2.22s    |
+--------------------+--------------------+-------------------+