Nonresponsive editor with large project when typescript.tsserver.watchOptions: vscode

[pelmers-db]

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

• VS Code Version: 1.96.2
• OS Version: Client = Macos 14.7, Remote = Linux 5.4

Steps to Reproduce:

1. Connect to remote ssh
2. Open a project with 20000+ .tsx files
3. Observe extreme slowness (5+ seconds to respond) with basic editor file actions: open file, save file, close file, etc.

Debugging notes:

1. when set typescript output to trace mode I see one watch event per file, e.g. [trace] <semantic> Event received: createFileWatcher (0). { "id": 364, "path": "/home/peter.elmers/fortesting/generated_tsx_project/src/Component10322.tsx" }
2. from reading code, looks like this hits the nonRecursiveWatcher which is nodejs: https://github.com/microsoft/vscode/blob/292d0bd51af8d7e107fa34b00955aceb7d9c03d5/src/vs/platform/files/node/watcher/watcher.ts/#L16-L17
3. all the watchers pile up and get sent to the nodejs watcher code, I believe that triggers a quadratic time loop in this function: https://github.com/microsoft/vscode/blob/292d0bd51af8d7e107fa34b00955aceb7d9c03d5/src/vs/platform/files/node/watcher/nodejs/nodejsWatcher.ts/#L45-L52

The issue seems to be that every time watchers change then we send in all of the watchers, so the watch code needs to loop through the list many times and find which ones to remove and which ones to keep. But this is just a cursory look.

cc @bpasero

[bpasero]

Is this project open source for us to reproduce?

[pelmers-db]

repro project: https://github.com/pelmers-db/lots-of-tsx-files-slow-vscode

the steps to repro:

1. open the project on remote linux
2. open a bunch of .tsx files by clicking in the file tree
3. observe vs code unresponsive

[bpasero]

@pelmers-db thanks, this issue is spot on, not only because I can reproduce but also because you actually found the perf issue in code 👏

In #237459 I am changing to a Map for lookups, both for non-recursive and recursive watchers (the latter is less likely to be a problem simply because typically there is not thousands of folders in a project, nor would TS watch as many folders).

After my fix, there is still a CPU spike but it settles rather quickly. Would be great if you could then confirm this fix in insiders when it lands tomorrow.

[vs-code-engineering]

This bug has been fixed in the latest release of VS Code Insiders!

@pelmers-db, you can help us out by commenting /verified if things are now working as expected.

If things still don't seem right, please ensure you're on version 2569d71 of Insiders (today's or later - you can use Help: About in the command palette to check), and leave a comment letting us know what isn't working as expected.

Happy Coding!

[bpasero]

I even found more optimisations thanks to your workspace:

• Drop need for expensive realcase: 6ac92b9
• watcher - defer realpath to only when needed #237600