use IdleTaskQueue & Date.now; some testcases

src/common/TaskQueue.ts

@@ -8,8 +8,11 @@ import { isNode } from 'common/Platform';
 interface ITaskQueue {
   /**
    * Adds a task to the queue which will run in a future idle callback.
+   * To avoid perceivable stalls on the mainthread, tasks with heavy workload
+   * should split their work into smaller pieces and return `true` to get
+   * called again until the work is done (on falsy return value).
    */
-  enqueue(task: () => void): void;
+  enqueue(task: () => boolean | void): void;
 
   /**
    * Flushes the queue, running all remaining tasks synchronously.
@@ -28,21 +31,23 @@ interface ITaskDeadline {
 type CallbackWithDeadline = (deadline: ITaskDeadline) => void;
 
 abstract class TaskQueue implements ITaskQueue {
-  private _tasks: (() => void)[] = [];
+  private _tasks: (() => boolean | void)[] = [];
   private _idleCallback?: number;
   private _i = 0;
 
   protected abstract _requestCallback(callback: CallbackWithDeadline): number;
   protected abstract _cancelCallback(identifier: number): void;
 
-  public enqueue(task: () => void): void {
+  public enqueue(task: () => boolean | void): void {
     this._tasks.push(task);
     this._start();
   }
 
   public flush(): void {
     while (this._i < this._tasks.length) {
-      this._tasks[this._i++]();
+      if (!this._tasks[this._i]()) {
+        this._i++;
+      }
     }
     this.clear();
   }
@@ -67,9 +72,14 @@ abstract class TaskQueue implements ITaskQueue {
     let taskDuration = 0;
     let longestTask = 0;
     while (this._i < this._tasks.length) {
-      taskDuration = performance.now();
-      this._tasks[this._i++]();
-      taskDuration = performance.now() - taskDuration;
+      taskDuration = Date.now();
+      if (!this._tasks[this._i]()) {
+        this._i++;
+      }
+      // other than performance.now, Date.now might not be stable (changes on wall clock changes),
+      // this is not an issue here as a clock change during a short running task is very unlikely
+      // in case it still happened and leads to negative duration, simply assume 1 msec
+      taskDuration = Math.max(1, Date.now() - taskDuration);
       longestTask = Math.max(taskDuration, longestTask);
       // Guess the following task will take a similar time to the longest task in this batch, allow
       // additional room to try avoid exceeding the deadline
@@ -97,9 +107,9 @@ export class PriorityTaskQueue extends TaskQueue {
   }
 
   private _createDeadline(duration: number): ITaskDeadline {
-    const end = performance.now() + duration;
+    const end = Date.now() + duration;
     return {
-      timeRemaining: () => Math.max(0, end - performance.now())
+      timeRemaining: () => Math.max(0, end - Date.now())
     };
   }
 }
@@ -136,7 +146,7 @@ export class DebouncedIdleTask {
     this._queue = new IdleTaskQueue();
   }
 
-  public set(task: () => void): void {
+  public set(task: () => boolean | void): void {
     this._queue.clear();
     this._queue.enqueue(task);
   }

src/common/buffer/Buffer.test.ts

@@ -9,6 +9,7 @@ import { CircularList } from 'common/CircularList';
 import { MockOptionsService, MockBufferService } from 'common/TestUtils.test';
 import { BufferLine, DEFAULT_ATTR_DATA } from 'common/buffer/BufferLine';
 import { CellData } from 'common/buffer/CellData';
+import { ExtendedAttrs } from 'common/buffer/AttributeData';
 
 const INIT_COLS = 80;
 const INIT_ROWS = 24;
@@ -1177,4 +1178,33 @@ describe('Buffer', () => {
       assert.equal(str3, '😁a');
     });
   });
+
+  describe('memory cleanup after shrinking', () => {
+    it('should realign memory from idle task execution', async () => {
+      buffer.fillViewportRows();
+
+      // shrink more than 2 times to trigger lazy memory cleanup
+      buffer.resize(INIT_COLS / 2 - 1, INIT_ROWS);
+
+      // sync
+      for (let i = 0; i < INIT_ROWS; i++) {
+        const line = buffer.lines.get(i)!;
+        // line memory is still at old size from initialization
+        assert.equal((line as any)._data.buffer.byteLength, INIT_COLS * 3 * 4);
+        // array.length and .length get immediately adjusted
+        assert.equal((line as any)._data.length, (INIT_COLS / 2 - 1) * 3);
+        assert.equal(line.length, INIT_COLS / 2 - 1);
+      }
+
+      // wait for a bit to give IdleTaskQueue a chance to kick in
+      // and finish memory cleaning
+      await new Promise(r => setTimeout(r, 100));
+
+      // cleanup should have realigned memory with exact bytelength
+      for (let i = 0; i < INIT_ROWS; i++) {
+        const line = buffer.lines.get(i)!;
+        assert.equal((line as any)._data.buffer.byteLength, (INIT_COLS / 2 - 1) * 3 * 4);
+      }
+    });
+  });
 });

src/common/buffer/Buffer.ts

@@ -14,7 +14,7 @@ import { Marker } from 'common/buffer/Marker';
 import { IOptionsService, IBufferService } from 'common/services/Services';
 import { DEFAULT_CHARSET } from 'common/data/Charsets';
 import { ExtendedAttrs } from 'common/buffer/AttributeData';
-import { DebouncedIdleTask } from 'common/TaskQueue';
+import { DebouncedIdleTask, IdleTaskQueue } from 'common/TaskQueue';
 
 export const MAX_BUFFER_SIZE = 4294967295; // 2^32 - 1
 
@@ -151,8 +151,8 @@ export class Buffer implements IBuffer {
     // store reference to null cell with default attrs
     const nullCell = this.getNullCell(DEFAULT_ATTR_DATA);
 
-    // defer memory cleanup of bufferlines
-    let needsCleanup = 0;
+    // count bufferlines with overly big memory to be cleaned afterwards
+    let dirtyMemoryLines = 0;
 
     // Increase max length if needed before adjustments to allow space to fill
     // as required.
@@ -168,7 +168,7 @@ export class Buffer implements IBuffer {
       if (this._cols < newCols) {
         for (let i = 0; i < this.lines.length; i++) {
           // +boolean for fast 0 or 1 conversion
-          needsCleanup |= +this.lines.get(i)!.resize(newCols, nullCell);
+          dirtyMemoryLines += +this.lines.get(i)!.resize(newCols, nullCell);
         }
       }
 
@@ -248,7 +248,7 @@ export class Buffer implements IBuffer {
       if (this._cols > newCols) {
         for (let i = 0; i < this.lines.length; i++) {
           // +boolean for fast 0 or 1 conversion
-          needsCleanup |= +this.lines.get(i)!.resize(newCols, nullCell);
+          dirtyMemoryLines += +this.lines.get(i)!.resize(newCols, nullCell);
         }
       }
     }
@@ -256,26 +256,33 @@ export class Buffer implements IBuffer {
     this._cols = newCols;
     this._rows = newRows;
 
-    if (needsCleanup) {
-      this._memoryCleanupTask.set(() => this._cleanupMemory());
-    } else {
-      // FIXME: DebouncedIdleTask has no clear method?
-      this._memoryCleanupTask.set(() => {});
+    this._memoryCleanupQueue.clear();
+    // schedule memory cleanup only, if more than 10% of the lines are affected
+    if (dirtyMemoryLines > 0.1 * this.lines.length) {
+      this._memoryCleanupQueue.enqueue(() => this._batchedMemoryCleanup());
     }
   }
 
-  private _memoryCleanupTask: DebouncedIdleTask = new DebouncedIdleTask();
+  private _memoryCleanupQueue = new IdleTaskQueue();
 
-  private _cleanupMemory(): void {
+  private _batchedMemoryCleanup(): boolean {
     let counted = 0;
     for (let i = 0; i < this.lines.length; i++) {
       counted += this.lines.get(i)!.cleanupMemory();
-      // throttle to 5k lines
+      // throttle to 5k lines at once and
+      // return true to indicate, that the task is not finished yet
       if (counted > 5000) {
-        this._memoryCleanupTask.set(() => this._cleanupMemory());
-        break;
+        return true;
       }
     }
+    return false;
+  }
+
+  private _forceMemoryCleanup(): void {
+    this._memoryCleanupQueue.clear();
+    for (let i = 0; i < this.lines.length; i++) {
+      this.lines.get(i)!.cleanupMemory();
+    }
   }
 
   private get _isReflowEnabled(): boolean {