Performance issue when opening multiple GitHub tabs with the Sourcegraph browser extension active

[taras-yemets]

We received a browser uninstall feedback reporting that having a few GitHub tabs opened with the Sourcegraph extension active consumes too much CPU resources.

[sourcegraph-bot-2]

Heads up @muratsu @rrhyne @jjinnii @ryankscott - the "team/growth-and-integrations" label was applied to this issue.

[vdavid]

I could reproduce it: Opened 6x the PR Keegan had opened and BExt CPU usage is now at 100%.
But I can’t reliably reproduce it.
The CPU was constantly up at 100% for my first try, until I closed some of the tabs.
Since then, I’ve tried opening 20+ tabs several times, and sometimes it doesn’t go over 20%, sometimes it goes to 100%, stays there for a few seconds, then drops.
If someone joins me who knows the BExt better, that helps, but I’ll try to look into it now.

[taras-yemets]

@philipp-spiess and I didn't manage to find a stable way to reproduce the issue.

Here's the debugging trace we got when we could reproduce it:

• We opened a few Chrome tabs with the same GitHub page having the Sourcegraph extension active.
• We opened a Task manager and noticed CPU usage of more than 100% by Sourcegraph extension dedicated workers:
• We recorded performance on the opened tabs in the extensions context and the browser context.
  • None of the performance recordings have a significant JavaScript load.
  • However we did notice a big chunk of unknown tasks in the browser context:
    
    • It's unclear how this was created and where this attributes to?
  • In one of the browser contexts we noticed a similar, unknown long-running task:
    

Here's a recording of the performance logs:

• Browser thread
• Extension thread