High CPU on large workspace with many TypeScript watched folders (fix microsoft#245366) (microsoft#245670)

* High CPU on large workspace with many TypeScript watched folders (fix microsoft#245366)

* reduce throttle delay

Author: bpasero

src/vs/base/common/async.ts

@@ -1303,6 +1303,7 @@ export class ThrottledWorker<T> extends Disposable {
 	override dispose(): void {
 		super.dispose();
 
+		this.pendingWork.length = 0;
 		this.disposed = true;
 	}
 }

src/vs/platform/files/node/watcher/nodejs/nodejsWatcher.ts

@@ -9,6 +9,8 @@ import { BaseWatcher } from '../baseWatcher.js';
 import { isLinux } from '../../../../../base/common/platform.js';
 import { INonRecursiveWatchRequest, INonRecursiveWatcher, IRecursiveWatcherWithSubscribe } from '../../../common/watcher.js';
 import { NodeJSFileWatcherLibrary } from './nodejsWatcherLib.js';
+import { ThrottledWorker } from '../../../../../base/common/async.js';
+import { MutableDisposable } from '../../../../../base/common/lifecycle.js';
 
 export interface INodeJSWatcherInstance {
 
@@ -30,6 +32,8 @@ export class NodeJSWatcher extends BaseWatcher implements INonRecursiveWatcher {
 	private readonly _watchers = new Map<string /* path */ | number /* correlation ID */, INodeJSWatcherInstance>();
 	get watchers() { return this._watchers.values(); }
 
+	private readonly worker = this._register(new MutableDisposable<ThrottledWorker<INonRecursiveWatchRequest>>());
+
 	constructor(protected readonly recursiveWatcher: IRecursiveWatcherWithSubscribe | undefined) {
 		super();
 	}
@@ -61,15 +65,36 @@ export class NodeJSWatcher extends BaseWatcher implements INonRecursiveWatcher {
 			this.trace(`Request to stop watching: ${Array.from(watchersToStop).map(watcher => this.requestToString(watcher.request)).join(',')}`);
 		}
 
+		// Stop the worker
+		this.worker.clear();
+
 		// Stop watching as instructed
 		for (const watcher of watchersToStop) {
 			this.stopWatching(watcher);
 		}
 
 		// Start watching as instructed
-		for (const request of requestsToStart) {
-			this.startWatching(request);
-		}
+		this.createWatchWorker().work(requestsToStart);
+	}
+
+	private createWatchWorker(): ThrottledWorker<INonRecursiveWatchRequest> {
+
+		// We see very large amount of non-recursive file watcher requests
+		// in large workspaces. To prevent the overhead of starting thousands
+		// of watchers at once, we use a throttled worker to distribute this
+		// work over time.
+
+		this.worker.value = new ThrottledWorker<INonRecursiveWatchRequest>({
+			maxWorkChunkSize: 100,				// only start 100 watchers at once before...
+			throttleDelay: 100,	  				// ...resting for 100ms until we start watchers again...
+			maxBufferedWork: Number.MAX_VALUE 	// ...and never refuse any work.
+		}, requests => {
+			for (const request of requests) {
+				this.startWatching(request);
+			}
+		});
+
+		return this.worker.value;
 	}
 
 	private requestToWatcherKey(request: INonRecursiveWatchRequest): string | number {

src/vs/platform/files/node/watcher/nodejs/nodejsWatcherLib.ts

@@ -183,6 +183,10 @@ export class NodeJSFileWatcherLibrary extends Disposable {
 	private async doWatchWithNodeJS(isDirectory: boolean, disposables: DisposableStore): Promise<void> {
 		const realPath = await this.realPath.value;
 
+		if (this.cts.token.isCancellationRequested) {
+			return;
+		}
+
 		// macOS: watching samba shares can crash VSCode so we do
 		// a simple check for the file path pointing to /Volumes
 		// (https://github.com/microsoft/vscode/issues/106879)
@@ -422,10 +426,12 @@ export class NodeJSFileWatcherLibrary extends Disposable {
 				}
 			});
 		} catch (error) {
-			if (!cts.token.isCancellationRequested) {
-				this.error(`Failed to watch ${realPath} for changes using fs.watch() (${error.toString()})`);
+			if (cts.token.isCancellationRequested) {
+				return;
 			}
 
+			this.error(`Failed to watch ${realPath} for changes using fs.watch() (${error.toString()})`);
+
 			this.notifyWatchFailed();
 		}
 	}