Jordan CosentinoOct 5, 2023

@siracusa While listening to @atpfm tonight I took the challenge. On an M1 Max MacBook Pro I opened 300 blank TextEdit windows before I started noticing some perceptible, but not egregious, lag. At 803 windows Window Server was using 7.56 GB of RAM (TextEdit ≈ 900MB) and was maxing out at least 1 CPU cores at all times. The entire machine was lagging and moving windows was extremely jumpy.

Edit: And single user account.

Show threadJohn Siracusa
@JAC151 Did you have more than one user logged in?
Oct 5, 2023 at 3:13amIvory for iOS
Show threadJordan CosentinoOct 5, 2023
@siracusa I did not. I have only one user on this particular machine.
Show threadJohn SiracusaOct 5, 2023
@JAC151 Add a second user and try it. (You can easily delete the user later.) You should tip over at closer to 300 windows instead of 800.
Show threadJordan CosentinoOct 5, 2023
@siracusa I added a second user and attempted this in both user accounts. All windows hidden except for TextEdit. At 191 windows there was noticeably more delay between pointer movement and window toolbar. At 346 it became just as unusable as the roughly 800 was before. Window Server is taking only 3.09 GB of RAM this time and the CPU usage is lower, but the lag and jumping is very much present. This is on macOS Sonoma.
Show threadJordan CosentinoOct 5, 2023
@siracusa I dropped it to 302 windows and the lag is there, but the jumpiness is greatly reduced. I moved it up to 325 windows and it's now incredibly jumpy (as is the Safari window). A second user definitely seems to lower the threshold. And attempting to drag windows in this state causes an extreme CPU spike.
Show threadJohn SiracusaOct 5, 2023
@JAC151 Hold down Option when dragging to remove the jumpiness, leaving only the lag. (Option disables the OS-level window snapping.)
Show threadJordan CosentinoOct 5, 2023

@siracusa Yes, that does indeed fix the jumpiness. I tried this experiment on both user accounts and the results were the same for roughly the same number of windows.

I believe this was also mentioned on the show, but hiding TextEdit with all 300+ windows seems to fix performance for all other visible windows immediately. However, as soon as I bring TextEdit back up everything comes to a halt.

Show threadJohn SiracusaOct 5, 2023
@JAC151 Yeah, I also mentioned that in my demo. Check it out if you want to see how bad it is with my Mac and my mouse and just ~25 windows. https://youtu.be/5Aq2GZpKkLU
FB13211706: Window dragging is laggy and jumpy when more than one user is logged in

YouTube
Show threadJohn SiracusaOct 5, 2023
@JAC151 A wired USB mouse and two logged in users should get you down to 150 windows for similar lag. It really is a wild bug!