Explorer rendering is slow

[jrieken]

re #15455

• close all editors, open explorer with ~50 files/folders visible
• add profiling instruction for viewlet restore (console.profile, console.profileEnd in https://github.com/Microsoft/vscode/blob/master/src/vs/workbench/electron-browser/workbench.ts#L289)
• reload the workbench
• 🐌 restoring the explorer takes ~450ms, 200ms of that time is spend in the tree, a significant amount of time is spend in FileLabel, ResourceLabel, IconLabel

CPU-20170105T174926.cpuprofile.zip

[bpasero]

@jrieken I am not seeing the same or any significant amount of time spend in the labels when I run. The labels should not have an impact on the number of folders expanded because they only kick in to the visible viewport of the tree. I also see some viewlet unrelated times in that profile (spawn, JSON??)

Attached is a trace of expanding every folder in the extensions directory of our source tree (including all of node_modules which gives a large test set).

Most of the time is spend in paths.isEqualOrParent which I am able to fix. Looking at the second trace (after my fix), most time is imho spend resolving files from disk and updating the tree (which is #18180).

Before:
CPU-20170112T081858_before.cpuprofile.zip

After:
CPU-20170112T081926_after.cpuprofile.zip

[jrieken]

I drilled very deep into the setInput and expandAll call found the renderer to take time (apart from the tree burning time). Unsure where I have seen the 200ms but I see this (in the original trace). Also looking in the traces

[jrieken]

Yeah, unsure where that time came from. With newer version I don't see it anymore. Maybe some dom-distorition effects?