1580116 - [macOS 10.15] High CPU utilization with many restored minimized windows

Status: RESOLVED DUPLICATE of bug 1580117

(Firefox :: Session Restore, defect)

Description

[Haik Aftandilian [:haik]]

Attachment: Test case basic HTML file loaded from ~/Desktop as a file:///

On macOS 10.15 Beta 7 (19A546d), I've noticed that with several windows minimized to the dock, when Firefox is restarted (with "Restore previous session" enabled), the Firefox parent process ("firefox") has very high CPU utilization. In my testing, the load was at least 40% for several minutes. For the tests below, I have ~50 windows minimized with each window having one tab with a static HTML file opened from ~/Desktop/basic.html. I first noticed this problem after restarting with ~10 windows minimized.

I have not tested on 10.14 or earlier releases.

Steps to reproduce:

1. Open 50 windows each with a single tab with the attached basic.html file loaded via file:/// from the filesystem
2. Minimize each window, leaving 1 remaining window
3. Enable "Restore previous session" in Firefox's preferences
4. Quit Firefox
5. Start Firefox
6. Check the CPU utilization of the firefox parent process (using $ top -o cpu).

Profiles collected:

1. https://perfht.ml/2ZONiqQ (after startup with ~50 windows minimized)
2. https://perfht.ml/2ZUqKVx (a second profile collected a few minutes later)
3. https://perfht.ml/2ZVHdZI (another instance of the problem after restarting the browser with ~50 minimized basic.html windows.)

After un-minimizing all ~50 minimized windows, %CPU utilization drops to 0%.

Comment 1

[Marcia Knous [:marcia]]

Duping this to Bug 1580117, as it appears this was duplicated when the bug was submitted.