UpdateProjectIfDirty is slow on large projects

[dbaeumer]

🔎 Search Terms

UpdateProjectIfDirty language server slow

🕗 Version & Regression Information

• tested the version that ships with VS Code

⏯ Playground Link

No response

💻 Code

Steps to reproduce:

• clone VS Code (https://github.com/microsoft/vscode.git)
• npm install
• open VS Code on the vscode repository
• open file task.constribution.ts
• open the TS server log
• add a new line to _ignoreEventForUpdateRunningTasksCount

Observe: updateGraphWorker takes roughly 300ms on my machine

I took a performance trace and a lot of time is spent in GC and getNormalizedAbsolutePath. I added a simply unbound cache to the method like

const pathCache = new Map();
function getNormalizedAbsolutePath(fileName, currentDirectory) {
  let cache = pathCache.get(currentDirectory);
  if (cache === undefined) {
    cache = new Map();
    pathCache.set(currentDirectory, cache);
  }
  let normalized = cache.get(fileName);
  if (normalized === undefined) {
    normalized = getPathFromPathComponents(getNormalizedPathComponents(fileName, currentDirectory));
    cache.set(fileName, normalized);
  }
  return normalized;
}

which cuts the time for updateGraphWorker in half. However there are still some GCs going on and a lot of time is now spent in verifyCompilerOptions / getNormalizedPathComponents.

🙁 Actual behavior

Takes 300ms to update on key stroke

🙂 Expected behavior

Adding a new line should be even in large project only cost a couple of ms :-)

Additional information about the issue

No response

[dbaeumer]

Doing a comparable cache in getNormalizedPathComponents brings the time down to 75ms.

vscode-profile-2024-11-28-09-36-24.cpuprofile
vscode-profile-2024-11-28-12-42-42.cpuprofile
vscode-profile-2024-11-28-15-29-10.cpuprofile

Here are also some of the CPU profiles I captured.