extension host consuming >300% CPU while no VSCode windows are open

[samuela]

Does this issue occur when all extensions are disabled?: No

• VS Code Version: 1.96.2 fabdb6a
• OS Version: macOS 15.1.1 (24B91)

Steps to Reproduce:

1. Open VSCode
2. Open Activity Monitor to notice consistent >300% CPU usage by a Code Helper (Plugin) process:

3. Inspect related processes with ps aux | grep 2040 to implicate the json-language-features extension:

❯ ps aux | grep 2040
samuelainsworth   2040 316.4  6.7 1631550720 4489488   ??  R    19Dec24 2740:22.41 /Applications/Visual Studio Code.app/Contents/Frameworks/Code Helper (Plugin).app/Contents/MacOS/Code Helper (Plugin) --type=utility --utility-sub-type=node.mojom.NodeService --lang=en-US --service-sandbox-type=none --dns-result-order=ipv4first --inspect-port=0 --user-data-dir=/Users/samuelainsworth/Library/Application Support/Code --standard-schemes=vscode-webview,vscode-file --enable-sandbox --secure-schemes=vscode-webview,vscode-file --cors-schemes=vscode-webview,vscode-file --fetch-schemes=vscode-webview,vscode-file --service-worker-schemes=vscode-webview --code-cache-schemes=vscode-webview,vscode-file --shared-files --field-trial-handle=1718379636,r,18016930961250905889,13590679581117912660,262144 --enable-features=ScreenCaptureKitPickerScreen,ScreenCaptureKitStreamPickerSonoma --disable-features=CalculateNativeWinOcclusion,MacWebContentsOcclusion,PlzDedicatedWorker,SpareRendererForSitePerProcess,TimeoutHangingVideoCaptureStarts --variations-seed-version
samuelainsworth   2152   0.0  0.1 1621845600  40848   ??  S    19Dec24   0:10.94 /Applications/Visual Studio Code.app/Contents/Frameworks/Code Helper (Plugin).app/Contents/MacOS/Code Helper (Plugin) /Applications/Visual Studio Code.app/Contents/Resources/app/extensions/json-language-features/server/dist/node/jsonServerMain --node-ipc --clientProcessId=2040
samuelainsworth   3918   0.0  0.0 410730496   4144 s011  S+    9:07PM   0:00.01 rg 2040

In particular, json-language-features/server/dist/node/jsonServerMain seems suspect.

[aeschli]

It's not the json-language-features process. The process that runs jsonServerMain has CPU 0.0.

Instead its the extension host process. So some extension(s) seem to be busy.

https://github.com/microsoft/vscode/wiki/Performance-Issues#visual-studio-code-is-consuming-a-lot-of-cpu
has more information on how to find the problematic extension. Can you have a look?

[samuela]

How do I view the cpu usage per extension? This behavior only comes on intermittently, so it's not clear how to bisect it.

[aeschli]

Once you see the issue happening you need to go to the 'Running Extensions' view and turn on 'Extension Host Profiling' (the record button in the view menu).

[samuela]

Gotcha, ok will do -- thanks! I'll close this and open a new issue if/when i can get that profiling data