MacOS – WindowServer high CPU usage, spikes when moving cursor on M1 MacBook Big Sur

cpum1macbook promacosmouse

The "WindowServer" process uses excessive CPU time on my 2020 M1 MacBook Pro running Big Sur 11.2.1. At idle it will sit at 15-25% CPU time. When moving the mouse cursor it jumps to 30-50% CPU time. This appears to cause some system slowdown under load and reduce battery life.

There are a few other threads and questions around the internet about high WindowServer CPU use but they're all for older MacOS versions on older Macs. I have tried some of the suggestions such as:

  • Looking for excessive logging from WindowServer and disabling those logs — there don't appear to be excessive logs
  • Turning on reduced transparency mode — no effect
  • Disabling apps that draw updates to the menu bar — no effect
  • Closing all apps except top in a terminal — no effect

So this appears to be a different issue perhaps specific to M1 Macs or to Big Sur. What might be causing this and how might it be mitigated?

Best Answer

Big Sur has many known issues related to UI performance. It’s almost certain that you’re experiencing one of these bugs, and so you’re unlikely to be able to do much about it yourself. We can try to confirm or refute this hypothesis if you’d like.

Does this occur if you’re running in Safe Mode? (Shift during boot) If so, do the following in Safe Mode. Otherwise, do it when the problem occurs.

  1. Run the following command to enable kernel symbolication: sudo nvram boot-args="keepsyms=1" (this may require you to disable SIP first).
  2. Reboot your machine and don’t open any apps except for Terminal.
  3. Do the minimum required in order to reproduce the problem.
  4. In Terminal, run the following, making sure you’re only running it during the window of time that you experience the system slowdown. (In particular, do NOT have Activity Monitor running when you do this.): sudo spindump -reveal -noProcessingWhileSampling
  5. After waiting for 10 seconds to collect a sample and another minute or two to symbolicate and format, you’ll get a file in /tmp/spindump.txt that contains a stackshot of every process.
  6. Upload the file to PasteBin or some equivalent place and we can take a look to see what’s causing the CPU usage spikes.
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