Fix memory cache (#762)

* Initial pass at fixing the memory cache

* Account for loading state in lru cache unload logic

* Remove nodes after the fact

* Simplify LRUCache eviction logic

* Add "loading" field for cache tiles

* Handle unloading correctly

* Remove log

* Don't try to dispose of any items above the max cache sizes unless we have tiles that are still loading

* Comment

* comments

* Comments

* Fix tests, ensure we only exit eviction loops when both size conditions are met

* Update tests

* Update LRUCache.js

Author: gkjohnson

src/base/TilesRendererBase.js

@@ -52,6 +52,11 @@ const lruPriorityCallback = ( a, b ) => {
 		// dispose of deeper tiles first
 		return a.__depthFromRenderedParent > b.__depthFromRenderedParent ? 1 : - 1;
 
+	} else if ( a.__loadingState !== b.__loadingState ) {
+
+		// dispose of tiles that are earlier along in the loading process first
+		return a.__loadingState > b.__loadingState ? - 1 : 1;
+
 	} else if ( a.__lastFrameVisited !== b.__lastFrameVisited ) {
 
 		// dispose of least recent tiles first
@@ -646,6 +651,7 @@ export class TilesRendererBase {
 				console.error( `TilesRenderer : Failed to load tile at url "${ tile.content.uri }".` );
 				console.error( e );
 				tile.__loadingState = FAILED;
+				lruCache.setLoaded( tile, true );
 
 			} else {
 
@@ -736,16 +742,24 @@ export class TilesRendererBase {
 
 				stats.parsing --;
 				tile.__loadingState = LOADED;
+				lruCache.setLoaded( tile, true );
 
-				// if the cache is full due to newly loaded memory then lets discard this tile - it will
-				// be loaded again later from the disk cache if needed.
-				if ( lruCache.isFull() ) {
+				// If the memory of the item hasn't been registered yet then that means the memory usage hasn't
+				// been accounted for by the cache yet so we need to check if it fits or if we should remove it.
+				if ( lruCache.getMemoryUsage( tile ) === null ) {
 
-					lruCache.remove( tile );
+					if ( lruCache.isFull() && lruCache.computeMemoryUsageCallback( tile ) > 0 ) {
 
-				} else {
+						// And if the cache is full due to newly loaded memory then lets discard this tile - it will
+						// be loaded again later from the disk cache if needed.
+						lruCache.remove( tile );
 
-					lruCache.updateMemoryUsage( tile );
+					} else {
+
+						// Otherwise update the item to the latest known value
+						lruCache.updateMemoryUsage( tile );
+
+					}
 
 				}
 

src/base/constants.js

@@ -1,8 +1,9 @@
+// FAILED is negative so lru cache priority sorting will unload it first
+export const FAILED = - 1;
 export const UNLOADED = 0;
 export const LOADING = 1;
 export const PARSING = 2;
 export const LOADED = 3;
-export const FAILED = 4;
 
 // https://en.wikipedia.org/wiki/World_Geodetic_System
 // https://en.wikipedia.org/wiki/Flattening

src/three/TilesRenderer.js

@@ -76,7 +76,7 @@ export class TilesRenderer extends TilesRendererBase {
 		this._eventDispatcher = new EventDispatcher();
 		this._upRotationMatrix = new Matrix4();
 
-		this.lruCache.getMemoryUsageCallback = tile => tile.cached.bytesUsed || 0;
+		this.lruCache.computeMemoryUsageCallback = tile => tile.cached.bytesUsed ?? null;
 
 		// flag indicating whether frustum culling should be disabled
 		this._autoDisableRendererCulling = true;

src/utilities/LRUCache.js

@@ -52,9 +52,10 @@ class LRUCache {
 		this.unloadingHandle = - 1;
 		this.cachedBytes = 0;
 		this.bytesMap = new Map();
+		this.loadedSet = new Set();
 
 		this._unloadPriorityCallback = null;
-		this.getMemoryUsageCallback = () => 0;
+		this.computeMemoryUsageCallback = () => null;
 
 		const itemSet = this.itemSet;
 		this.defaultPriorityCallback = item => itemSet.get( item );
@@ -68,6 +69,12 @@ class LRUCache {
 
 	}
 
+	getMemoryUsage( item ) {
+
+		return this.bytesMap.get( item ) ?? null;
+
+	}
+
 	add( item, removeCb ) {
 
 		if ( this.markUnusedQueued ) {
@@ -98,8 +105,9 @@ class LRUCache {
 		itemSet.set( item, Date.now() );
 		callbacks.set( item, removeCb );
 
-		const bytes = this.getMemoryUsageCallback( item );
-		this.cachedBytes += bytes;
+		// computeMemoryUsageCallback can return "null" if memory usage is not known, yet
+		const bytes = this.computeMemoryUsageCallback( item );
+		this.cachedBytes += bytes || 0;
 		bytesMap.set( item, bytes );
 
 		return true;
@@ -113,10 +121,11 @@ class LRUCache {
 		const itemList = this.itemList;
 		const bytesMap = this.bytesMap;
 		const callbacks = this.callbacks;
+		const loadedSet = this.loadedSet;
 
 		if ( itemSet.has( item ) ) {
 
-			this.cachedBytes -= bytesMap.get( item );
+			this.cachedBytes -= bytesMap.get( item ) || 0;
 			bytesMap.delete( item );
 
 			callbacks.get( item )( item );
@@ -126,6 +135,7 @@ class LRUCache {
 			usedSet.delete( item );
 			itemSet.delete( item );
 			callbacks.delete( item );
+			loadedSet.delete( item );
 
 			return true;
 
@@ -135,6 +145,28 @@ class LRUCache {
 
 	}
 
+	// Marks whether tiles in the cache have been completely loaded or not. Tiles that have not been completely
+	// loaded are subject to being disposed early if the cache is full above its max size limits, even if they
+	// are marked as used.
+	setLoaded( item, value ) {
+
+		const { itemSet, loadedSet } = this;
+		if ( itemSet.has( item ) ) {
+
+			if ( value === true ) {
+
+				loadedSet.add( item );
+
+			} else {
+
+				loadedSet.delete( item );
+
+			}
+
+		}
+
+	}
+
 	updateMemoryUsage( item ) {
 
 		const itemSet = this.itemSet;
@@ -145,9 +177,9 @@ class LRUCache {
 
 		}
 
-		this.cachedBytes -= bytesMap.get( item );
+		this.cachedBytes -= bytesMap.get( item ) || 0;
 
-		const bytes = this.getMemoryUsageCallback( item );
+		const bytes = this.computeMemoryUsageCallback( item );
 		bytesMap.set( item, bytes );
 		this.cachedBytes += bytes;
 
@@ -196,32 +228,44 @@ class LRUCache {
 			itemList,
 			itemSet,
 			usedSet,
+			loadedSet,
 			callbacks,
 			bytesMap,
 			minBytesSize,
 			maxBytesSize,
 		} = this;
 
 		const unused = itemList.length - usedSet.size;
+		const unloaded = itemList.length - loadedSet.size;
 		const excessNodes = Math.max( Math.min( itemList.length - minSize, unused ), 0 );
 		const excessBytes = this.cachedBytes - minBytesSize;
 		const unloadPriorityCallback = this.unloadPriorityCallback || this.defaultPriorityCallback;
 		let needsRerun = false;
 
-		const hasNodesToUnload = excessNodes > 0 && unused > 0 || itemList.length > maxSize;
-		const hasBytesToUnload = unused && this.cachedBytes > minBytesSize || this.cachedBytes > maxBytesSize;
+		const hasNodesToUnload = excessNodes > 0 && unused > 0 || unloaded && itemList.length > maxSize;
+		const hasBytesToUnload = unused && this.cachedBytes > minBytesSize || unloaded && this.cachedBytes > maxBytesSize;
 		if ( hasBytesToUnload || hasNodesToUnload ) {
 
-			// used items should be at the end of the array
+			// used items should be at the end of the array, "unloaded" items in the middle of the array
 			itemList.sort( ( a, b ) => {
 
 				const usedA = usedSet.has( a );
 				const usedB = usedSet.has( b );
 				if ( usedA === usedB ) {
 
-					// Use the sort function otherwise
-					// higher priority should be further to the left
-					return - unloadPriorityCallback( a, b );
+					const loadedA = loadedSet.has( a );
+					const loadedB = loadedSet.has( b );
+					if ( loadedA === loadedB ) {
+
+						// Use the sort function otherwise
+						// higher priority should be further to the left
+						return - unloadPriorityCallback( a, b );
+
+					} else {
+
+						return loadedA ? 1 : - 1;
+
+					}
 
 				} else {
 
@@ -241,27 +285,44 @@ class LRUCache {
 
 			let removedNodes = 0;
 			let removedBytes = 0;
-			while ( true ) {
+
+			// evict up to the max node or bytes size, keeping one more item over the max bytes limit
+			// so the "full" function behaves correctly.
+			while (
+				this.cachedBytes - removedBytes > maxBytesSize ||
+				itemList.length - removedNodes > maxSize
+			) {
 
 				const item = itemList[ removedNodes ];
-				const bytes = bytesMap.get( item );
+				const bytes = bytesMap.get( item ) || 0;
+				if (
+					usedSet.has( item ) && loadedSet.has( item ) ||
+					this.cachedBytes - removedBytes - bytes < maxBytesSize &&
+					itemList.length - removedNodes <= maxSize
+				) {
 
-				// note that these conditions ensure we keep one tile over the byte cap so we can
-				// align with the the isFull function reports.
+					break;
+
+				}
+
+				removedBytes += bytes;
+				removedNodes ++;
+
+			}
 
-				// base while condition
-				const doContinue =
-					removedNodes < nodesToUnload
-					|| removedBytes < bytesToUnload
-					|| this.cachedBytes - removedBytes - bytes > maxBytesSize
-					|| itemList.length - removedNodes > maxSize;
+			// evict up to the min node or bytes size, keeping one more item over the min bytes limit
+			// so we're meeting it
+			while (
+				removedBytes < bytesToUnload ||
+				removedNodes < nodesToUnload
+			) {
 
-				// don't unload any used tiles unless we're above our size cap
+				const item = itemList[ removedNodes ];
+				const bytes = bytesMap.get( item ) || 0;
 				if (
-					! doContinue
-					|| removedNodes >= unused
-					&& this.cachedBytes - removedBytes - bytes <= maxBytesSize
-					&& itemList.length - removedNodes <= maxSize
+					usedSet.has( item ) ||
+					this.cachedBytes - removedBytes - bytes < minBytesSize &&
+					removedNodes >= nodesToUnload
 				) {
 
 					break;
@@ -271,15 +332,21 @@ class LRUCache {
 				removedBytes += bytes;
 				removedNodes ++;
 
-				bytesMap.delete( item );
+			}
+
+			// remove the nodes
+			itemList.splice( 0, removedNodes ).forEach( item => {
+
+				this.cachedBytes -= bytesMap.get( item ) || 0;
+
 				callbacks.get( item )( item );
+				bytesMap.delete( item );
 				itemSet.delete( item );
 				callbacks.delete( item );
+				loadedSet.delete( item );
+				usedSet.delete( item );
 
-			}
-
-			itemList.splice( 0, removedNodes );
-			this.cachedBytes -= removedBytes;
+			} );
 
 			// if we didn't remove enough nodes or we still have excess bytes and there are nodes to removed
 			// then we want to fire another round of unloading