Slow to switch to/from tab with large collapsed section

[ghost]

• VSCode Version: Code - Insiders 1.16.0-insider (dc3a6df, 2017-08-11T07:07:15.518Z)
• OS Version: Windows_NT x64 10.0.15063
• Extensions: none

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Steps to Reproduce:

1. New empty directory
2. npm install @types/lodash
3. Create a file a.ts containing _.add(1, 2)
4. Go to definition on _ to get taken to node_modules/@types/lodash/index.d.ts
5. Collapse the declare namespace _ section, which spans nearly 20000 lines.
6. Go back to the tab from a.ts, then back to index.d.ts, repeat. It's noticeably slow. No issue if you uncollapse everything.

[bpasero]

I think in this case a CPU profile would help:

To create a CPU profile using developer tools in VS Code:

• select Help > Toggle Developer Tools
• click on Profiles
• click the start button
• do whatever you need to do to get the CPU spin high
• wait for some time (10-20 seconds should be enough)
• stop the profiling
• click the save button and attach the output file to this issue

[ghost]

OK, here it is:
CPU-20170811T083908.zip

[aeschli]

Trace when the the editor that shows index.d.ts gets active.
Note how the decoration are all computed in 'setModel', disposed and recomputed again in 'restoreViewState'.

@sandy081 You made these changes in de73151.
Do you remember why?

[aeschli]

@sandy081 I changed the code of restoreViewState to no longer rebuild the folded ranges. Looks like the settings default editor no longer requires that anyway.

[sandy081]

@aeschli Yes that was done to restore the folding state of default settings editor which is not the case anymore.

[rodrigobutta]

Same problem here. Switching tabs and i think almost everything is having a slow response since a few days ago, My pc has an I7, 12GB RAB and SSD. Windows 10, 64.