add gpu timing map events (#8829)

* Introduce 'gpuTiming' map options.

Originally implemented by Chris. I've rebased it and exposed it
with just the event listeners instead of a map option.

Listen to `gpu-timing-frame` to get the gpu time for the frame and
listen to `gpu-timing-layer` to get the gpu time for all individual
layers. It is not recommended to listen to both.

* fixup

src/gl/context.js

@@ -63,6 +63,7 @@ class Context {
     extTextureFilterAnisotropic: any;
     extTextureFilterAnisotropicMax: any;
     extTextureHalfFloat: any;
+    extTimerQuery: any;
 
     constructor(gl: WebGLRenderingContext) {
         this.gl = gl;
@@ -113,6 +114,8 @@ class Context {
         if (this.extTextureHalfFloat) {
             gl.getExtension('OES_texture_half_float_linear');
         }
+
+        this.extTimerQuery = gl.getExtension('EXT_disjoint_timer_query');
     }
 
     setDefault() {

src/render/painter.js

@@ -73,6 +73,7 @@ type PainterOptions = {
     rotating: boolean,
     zooming: boolean,
     moving: boolean,
+    gpuTiming: boolean,
     fadeDuration: number
 }
 
@@ -121,6 +122,7 @@ class Painter {
     cache: { [string]: Program<*> };
     crossTileSymbolIndex: CrossTileSymbolIndex;
     symbolFadeChange: number;
+    gpuTimers: { [string]: any };
 
     constructor(gl: WebGLRenderingContext, transform: Transform) {
         this.context = new Context(gl);
@@ -139,6 +141,8 @@ class Painter {
         this.emptyProgramConfiguration = new ProgramConfiguration();
 
         this.crossTileSymbolIndex = new CrossTileSymbolIndex();
+
+        this.gpuTimers = {};
     }
 
     /*
@@ -469,7 +473,52 @@ class Painter {
         if (layer.type !== 'background' && layer.type !== 'custom' && !coords.length) return;
         this.id = layer.id;
 
+        this.gpuTimingStart(layer);
         draw[layer.type](painter, sourceCache, layer, coords, this.style.placement.variableOffsets);
+        this.gpuTimingEnd();
+    }
+
+    gpuTimingStart(layer: StyleLayer) {
+        if (!this.options.gpuTiming) return;
+        const ext = this.context.extTimerQuery;
+        // This tries to time the draw call itself, but note that the cost for drawing a layer
+        // may be dominated by the cost of uploading vertices to the GPU.
+        // To instrument that, we'd need to pass the layerTimers object down into the bucket
+        // uploading logic.
+        let layerTimer = this.gpuTimers[layer.id];
+        if (!layerTimer) {
+            layerTimer = this.gpuTimers[layer.id] = {
+                calls: 0,
+                cpuTime: 0,
+                query: ext.createQueryEXT()
+            };
+        }
+        layerTimer.calls++;
+        ext.beginQueryEXT(ext.TIME_ELAPSED_EXT, layerTimer.query);
+    }
+
+    gpuTimingEnd() {
+        if (!this.options.gpuTiming) return;
+        const ext = this.context.extTimerQuery;
+        ext.endQueryEXT(ext.TIME_ELAPSED_EXT);
+    }
+
+    collectGpuTimers() {
+        const currentLayerTimers = this.gpuTimers;
+        this.gpuTimers = {};
+        return currentLayerTimers;
+    }
+
+    queryGpuTimers(gpuTimers: {[string]: any}) {
+        const layers = {};
+        for (const layerId in gpuTimers) {
+            const gpuTimer = gpuTimers[layerId];
+            const ext = this.context.extTimerQuery;
+            const gpuTime = ext.getQueryObjectEXT(gpuTimer.query, ext.QUERY_RESULT_EXT) / (1000 * 1000);
+            ext.deleteQueryEXT(gpuTimer.query);
+            layers[layerId] = gpuTime;
+        }
+        return layers;
     }
 
     /**

src/ui/map.js

@@ -1938,6 +1938,14 @@ class Map extends Camera {
      * @private
      */
     _render() {
+        let gpuTimer, frameStartTime = 0;
+        const extTimerQuery = this.painter.context.extTimerQuery;
+        if (this.listens('gpu-timing-frame')) {
+            gpuTimer = extTimerQuery.createQueryEXT();
+            extTimerQuery.beginQueryEXT(extTimerQuery.TIME_ELAPSED_EXT, gpuTimer);
+            frameStartTime = browser.now();
+        }
+
         // A custom layer may have used the context asynchronously. Mark the state as dirty.
         this.painter.context.setDirty();
         this.painter.setBaseState();
@@ -1989,6 +1997,7 @@ class Map extends Camera {
             rotating: this.isRotating(),
             zooming: this.isZooming(),
             moving: this.isMoving(),
+            gpuTiming: !!this.listens('gpu-timing-layer'),
             fadeDuration: this._fadeDuration
         });
 
@@ -2010,6 +2019,33 @@ class Map extends Camera {
             this.style._releaseSymbolFadeTiles();
         }
 
+        if (this.listens('gpu-timing-frame')) {
+            const renderCPUTime = browser.now() - frameStartTime;
+            extTimerQuery.endQueryEXT(extTimerQuery.TIME_ELAPSED_EXT, gpuTimer);
+            setTimeout(() => {
+                const renderGPUTime = extTimerQuery.getQueryObjectEXT(gpuTimer, extTimerQuery.QUERY_RESULT_EXT) / (1000 * 1000);
+                extTimerQuery.deleteQueryEXT(gpuTimer);
+                this.fire(new Event('gpu-timing-frame', {
+                    cpuTime: renderCPUTime,
+                    gpuTime: renderGPUTime
+                }));
+            }, 50); // Wait 50ms to give time for all GPU calls to finish before querying
+        }
+
+        if (this.listens('gpu-timing-layer')) {
+            // Resetting the Painter's per-layer timing queries here allows us to isolate
+            // the queries to individual frames.
+            const frameLayerQueries = this.painter.collectGpuTimers();
+
+            setTimeout(() => {
+                const renderedLayerTimes = this.painter.queryGpuTimers(frameLayerQueries);
+
+                this.fire(new Event('gpu-timing-layer', {
+                    layerTimes: renderedLayerTimes
+                }));
+            }, 50); // Wait 50ms to give time for all GPU calls to finish before querying
+        }
+
         // Schedule another render frame if it's needed.
         //
         // Even though `_styleDirty` and `_sourcesDirty` are reset in this
@@ -2020,6 +2056,7 @@ class Map extends Camera {
         } else if (!this.isMoving() && this.loaded()) {
             this.fire(new Event('idle'));
         }
+
         return this;
     }