Jupyterlab Tab Close Performance

[mlucool]

Description

Similar to switching tabs (jupyterlab/jupyterlab#4292) and opening notebooks, closing notebooks is slow.

Reproduce

Open a notebook with 1k cells.

The performance graph looks like this when closing it (all the purple at the bottom is another forced reflow):

Expected behavior

It closes even faster than it opens

Context

• Operating System and version: Linux
• Browser and version: Chrome
• JupyterLab version: 3.1.x

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[fcollonval]

Hey @mlucool

I was looking at analyzing that case. But for me the waterfall is looking quite differently:

Ref:

• Chromium 90 on Debian 11
• JupyterLab 3.1.10

The test notebook is a 157 identical cells notebook without outputs.

Common cell print 300 times a two-lines string

for x in range(OUTPUT_LENGTH):
    print(f'{PREFIX} {x}')