stray Python processes when running mypy, maxing out CPU completely

[brettcannon]

Discussed in #20517

^{Originally posted by ThomasEwaldETH January 16, 2023}
Hello there!

Since of today, my Python extension in Visual Studio Code maxes out my CPU. I recently had this issue (maybe a week ago), where I could solve it with
https://stackoverflow.com/questions/71516186/vs-code-uses-100-cpu-even-if-it-is-closed

It worked for a couple of days now. However, as of today, I am quickly again at 100% CPU. Here a couple of things I recognized so far:

• When I start VSC, a Python sub process is generated, which takes up about 25-40% of CPU. This sub process does not get terminated. When it is active, the extension does not work properly, meaning that for example linting does not work. If I terminate it manually, linting immediately works. After terminating, VSC goes down to 0% CPU usage.
• The moment I press 'save' (strg+s) in an arbitrary file in my Python project folder, two sub processes are created: One also taking up 25-40%, the other one quickly going down to zero, but doesn't get terminated. In addition, all linting highlights are gone and the linting seems to not work anymore.
• If I press 'save' a second time (no matter which file I'm in), two new sub processes are created. Again, one quickly falling down to zero, the other one taking up another 25-40% of CPU -> consequently, if I press 'save' four times, my CPU is maxed out.
• If I terminate the CPU draining sub processes, the 'dead' ones with 0% CPU seem to get terminated after a short while.
• I have ALWAYS two 0% CPU sub processes running that are named 'Python'.

In the following a couple of snippets from my Task Manager:

Here, the CPU usage after starting VSC, where the project folder is opened automatically.

Terminated the first sub process manually - remaining two 0% sub processes.

Hit 'save' a single time.

Hit 'save' a second time. And so on...

I am using Win11, about my VSC:
Version: 1.74.3 (user setup)
Commit: 97dec172d3256f8ca4bfb2143f3f76b503ca0534
Date: 2023-01-09T16:59:02.252Z
Electron: 19.1.8
Chromium: 102.0.5005.167
Node.js: 16.14.2
V8: 10.2.154.15-electron.0
OS: Windows_NT x64 10.0.22621
Sandboxed: No

I am completely out of ideas on how to get this fixed, since it just appeared out of nowhere today. Maybe someone here has an idea. Searching with Google didn't provide a lot, aside from what I linked above.

I would be grateful for help!
Best regards,
Thomas

[brettcannon]

Figured out it was mypy in #20517 (reply in thread) .

[brettcannon]

/cc Thomas Ewald (@ThomasEwaldETH)

[XiaoHuiHui233]

Hi everyone, I also ran into this problem today during my work. I've never used mypy support in the past, and have always run mypy manually to check my codes. Accidentally I opened the mypy linting of the Python plugin of my VSCode today, and after about half an hour this problem happened. My VSCode is running on WSL, and I use my Macbook to remote access it. I have autosave turned on. I use htop to monitor background processes on my WSL and find that the process of python -m mypy will be generated after each save. These processes are running all the time. Once I modify my code frequently and save it automatically, there will be a large number of mypy processes occupying my system, which will eventually cause my CPU(by the way, its 5900X) and memory usage to be fully loaded. I closed VSCode and it didn't make these processes disappear, and finally I had to execute killall python to kill all these processes. This is an incredible problem, and I wouldn't consider enabling mypy support again until this problem is identified and fixed.

[karthiknadig]

We now have a preview version of mypy extension that uses dmypy for linting. Please give it a try:
https://marketplace.visualstudio.com/items?itemName=ms-python.mypy-type-checker

[ThomasEwaldETH]

Thanks a lot! I will try it.
Best regards

[karthiknadig]

Use https://marketplace.visualstudio.com/items?itemName=ms-python.mypy-type-checker we have made the first stable release of this extension.

[ThomasEwaldETH]

Thanks a lot! Best regards