[perf] tags pool experiment

packages/@glimmer/runtime/lib/environment.ts

@@ -14,7 +14,7 @@ import type {
 } from '@glimmer/interfaces';
 import { RuntimeProgramImpl } from '@glimmer/program';
 import { assert, expect } from '@glimmer/util';
-import { track, updateTag } from '@glimmer/validator';
+import { prepareTagsIfNeeded, track, updateTag } from '@glimmer/validator';
 
 import DebugRenderTree from './debug-render-tree';
 import { DOMChangesImpl, DOMTreeConstruction } from './dom/helper';
@@ -137,6 +137,9 @@ export class EnvironmentImpl implements Environment {
       'A glimmer transaction was begun, but one already exists. You may have a nested transaction, possibly caused by an earlier runtime exception while rendering. Please check your console for the stack trace of any prior exceptions.'
     );
 
+    setTimeout(() => {
+      prepareTagsIfNeeded();
+    });
     this.debugRenderTree?.begin();
 
     this[TRANSACTION] = new TransactionImpl();

packages/@glimmer/validator/index.ts

@@ -44,6 +44,7 @@ export {
   DIRTY_TAG as dirtyTag,
   INITIAL,
   isConstTag,
+  prepareTagsIfNeeded,
   type Revision,
   UPDATE_TAG as updateTag,
   validateTag,

packages/@glimmer/validator/lib/tracking.ts

@@ -6,6 +6,11 @@ import { debug } from './debug';
 import { unwrap } from './utils';
 import { combine, CONSTANT_TAG, isConstTag, validateTag, valueForTag } from './validators';
 
+const TRACKING_WARM_STACK_SIZE = 20000;
+
+function getTracker() {
+  return trackingStack.pop() ?? new Tracker();
+}
 /**
  * An object that that tracks @tracked properties that were consumed.
  */
@@ -36,8 +41,16 @@ class Tracker {
       return combine(Array.from(this.tags));
     }
   }
+  recycle() {
+    this.tags.clear();
+    trackingStack.push(this);
+  }
 }
 
+const trackingStack: Tracker[] = new Array(TRACKING_WARM_STACK_SIZE)
+  .fill(null)
+  .map(() => new Tracker());
+
 /**
  * Whenever a tracked computed property is entered, the current tracker is
  * saved off and a new tracker is replaced.
@@ -58,7 +71,7 @@ const OPEN_TRACK_FRAMES: (Tracker | null)[] = [];
 export function beginTrackFrame(debuggingContext?: string | false): void {
   OPEN_TRACK_FRAMES.push(CURRENT_TRACKER);
 
-  CURRENT_TRACKER = new Tracker();
+  CURRENT_TRACKER = getTracker();
 
   if (import.meta.env.DEV) {
     unwrap(debug.beginTrackingTransaction)(debuggingContext);
@@ -78,7 +91,11 @@ export function endTrackFrame(): Tag {
 
   CURRENT_TRACKER = OPEN_TRACK_FRAMES.pop() || null;
 
-  return unwrap(current).combine();
+  try {
+    return unwrap(current).combine();
+  } finally {
+    current!.recycle();
+  }
 }
 
 export function beginUntrackFrame(): void {

packages/@glimmer/validator/lib/validators.ts

@@ -28,6 +28,11 @@ export const VOLATILE: Revision = NaN;
 
 export let $REVISION = INITIAL;
 
+const UPDATABLE_TAG_WARM_CHUNK_SIZE = 1000;
+const UPDATABLE_TAG_WARM_STACK_SIZE = UPDATABLE_TAG_WARM_CHUNK_SIZE * 20;
+const DIRTYABLE_TAG_WARM_CHUNK_SIZE = 1000;
+const DIRTYABLE_TAG_WARM_STACK_SIZE = DIRTYABLE_TAG_WARM_CHUNK_SIZE * 20;
+
 export function bump(): void {
   $REVISION++;
 }
@@ -39,8 +44,6 @@ const UPDATABLE_TAG_ID: IUPDATABLE_TAG_ID = 1;
 const COMBINATOR_TAG_ID: ICOMBINATOR_TAG_ID = 2;
 const CONSTANT_TAG_ID: ICONSTANT_TAG_ID = 3;
 
-//////////
-
 export const COMPUTE: TagComputeSymbol = Symbol('TAG_COMPUTE') as TagComputeSymbol;
 
 //////////
@@ -90,6 +93,19 @@ function allowsCycles(tag: Tag): boolean {
   }
 }
 
+export function prepareTagsIfNeeded() {
+  if (UPDATABLE_TAGS.length < UPDATABLE_TAG_WARM_CHUNK_SIZE) {
+    for (let i = 0; i < UPDATABLE_TAG_WARM_CHUNK_SIZE; i++) {
+      UPDATABLE_TAGS.push(new MonomorphicTagImpl(UPDATABLE_TAG_ID));
+    }
+  }
+  if (DIRYTABLE_TAGS.length < DIRTYABLE_TAG_WARM_CHUNK_SIZE) {
+    for (let i = 0; i < DIRTYABLE_TAG_WARM_CHUNK_SIZE; i++) {
+      DIRYTABLE_TAGS.push(new MonomorphicTagImpl(DIRYTABLE_TAG_ID));
+    }
+  }
+}
+
 class MonomorphicTagImpl<T extends MonomorphicTagId = MonomorphicTagId> {
   static combine(this: void, tags: Tag[]): Tag {
     switch (tags.length) {
@@ -222,17 +238,28 @@ class MonomorphicTagImpl<T extends MonomorphicTagId = MonomorphicTagId> {
   }
 }
 
+//////////
+
+const UPDATABLE_TAGS: UpdatableTag[] = new Array(UPDATABLE_TAG_WARM_STACK_SIZE)
+  .fill(null)
+  .map(() => new MonomorphicTagImpl(1 as IUPDATABLE_TAG_ID));
+const DIRYTABLE_TAGS: DirtyableTag[] = new Array(DIRTYABLE_TAG_WARM_STACK_SIZE)
+  .fill(null)
+  .map(() => new MonomorphicTagImpl(0 as IDIRTYABLE_TAG_ID));
+
+//////////
+
 export const DIRTY_TAG = MonomorphicTagImpl.dirtyTag;
 export const UPDATE_TAG = MonomorphicTagImpl.updateTag;
 
 //////////
 
 export function createTag(): DirtyableTag {
-  return new MonomorphicTagImpl(DIRYTABLE_TAG_ID);
+  return DIRYTABLE_TAGS.pop() ?? new MonomorphicTagImpl(DIRYTABLE_TAG_ID);
 }
 
 export function createUpdatableTag(): UpdatableTag {
-  return new MonomorphicTagImpl(UPDATABLE_TAG_ID);
+  return UPDATABLE_TAGS.pop() ?? new MonomorphicTagImpl(UPDATABLE_TAG_ID);
 }
 
 //////////