core(estimated-input-latency): use a 5s rolling window

lighthouse-core/audits/estimated-input-latency.js

@@ -10,6 +10,8 @@ const Util = require('../report/v2/renderer/util');
 const TracingProcessor = require('../lib/traces/tracing-processor');
 const LHError = require('../lib/errors');
 
+const ROLLING_WINDOW_SIZE = 5000;
+
 class EstimatedInputLatency extends Audit {
   /**
    * @return {!AuditMeta}
@@ -19,8 +21,7 @@ class EstimatedInputLatency extends Audit {
       name: 'estimated-input-latency',
       description: 'Estimated Input Latency',
       helpText: 'The score above is an estimate of how long your app takes to respond to user ' +
-          'input, in milliseconds. There is a 90% probability that a user encounters this amount ' +
-          'of latency, or less. 10% of the time a user can expect additional latency. If your ' +
+          'input, in milliseconds, during the busiest 5s window of page load. If your ' +
           'latency is higher than 50 ms, users may perceive your app as laggy. ' +
           '[Learn more](https://developers.google.com/web/tools/lighthouse/audits/estimated-input-latency).',
       scoreDisplayMode: Audit.SCORING_MODES.NUMERIC,
@@ -45,23 +46,36 @@ class EstimatedInputLatency extends Audit {
       throw new LHError(LHError.errors.NO_FMP);
     }
 
-    const latencyPercentiles = TracingProcessor.getRiskToResponsiveness(tabTrace, startTime);
-    const ninetieth = latencyPercentiles.find(result => result.percentile === 0.9);
-    const rawValue = parseFloat(ninetieth.time.toFixed(1));
+    const events = TracingProcessor.getMainThreadTopLevelEvents(tabTrace, startTime)
+      .filter(evt => evt.duration >= 1);
+
+    const candidateStartEvts = events.filter(evt => evt.duration >= 10);
+
+    let worst90thPercentileLatency = 16;
+    for (const startEvt of candidateStartEvts) {
+      const latencyPercentiles = TracingProcessor.getRiskToResponsiveness(
+        events,
+        startEvt.start,
+        startEvt.start + ROLLING_WINDOW_SIZE,
+        [0.9]
+      );
+
+      worst90thPercentileLatency = Math.max(
+        latencyPercentiles[0].time,
+        worst90thPercentileLatency
+      );
+    }
 
     const score = Audit.computeLogNormalScore(
-      ninetieth.time,
+      worst90thPercentileLatency,
       context.options.scorePODR,
       context.options.scoreMedian
     );
 
     return {
       score,
-      rawValue,
-      displayValue: Util.formatMilliseconds(rawValue, 1),
-      extendedInfo: {
-        value: latencyPercentiles,
-      },
+      rawValue: worst90thPercentileLatency,
+      displayValue: Util.formatMilliseconds(worst90thPercentileLatency, 1),
     };
   }
 

lighthouse-core/lib/traces/tracing-processor.js

@@ -84,42 +84,44 @@ class TraceProcessor {
    * Calculates the maximum queueing time (in ms) of high priority tasks for
    * selected percentiles within a window of the main thread.
    * @see https://docs.google.com/document/d/1b9slyaB9yho91YTOkAQfpCdULFkZM9LqsipcX3t7He8/preview
-   * @param {LH.Artifacts.TraceOfTab} tabTrace
-   * @param {number=} startTime Optional start time (in ms relative to navstart) of range of interest. Defaults to navstart.
-   * @param {number=} endTime Optional end time (in ms relative to navstart) of range of interest. Defaults to trace end.
+   * @param {Array<ToplevelEvent>} events
+   * @param {number} startTime Start time (in ms relative to navstart) of range of interest.
+   * @param {number} endTime End time (in ms relative to navstart) of range of interest.
    * @param {!Array<number>=} percentiles Optional array of percentiles to compute. Defaults to [0.5, 0.75, 0.9, 0.99, 1].
    * @return {!Array<{percentile: number, time: number}>}
    */
   static getRiskToResponsiveness(
-      tabTrace,
-      startTime = 0,
-      endTime = tabTrace.timings.traceEnd,
+      events,
+      startTime,
+      endTime,
       percentiles = [0.5, 0.75, 0.9, 0.99, 1]
   ) {
     const totalTime = endTime - startTime;
     percentiles.sort((a, b) => a - b);
 
-    const ret = TraceProcessor.getMainThreadTopLevelEventDurations(tabTrace, startTime, endTime);
+    const ret = TraceProcessor.getMainThreadTopLevelEventDurations(events, startTime, endTime);
     return TraceProcessor._riskPercentiles(ret.durations, totalTime, percentiles,
         ret.clippedLength);
   }
 
   /**
    * Provides durations in ms of all main thread top-level events
-   * @param {LH.Artifacts.TraceOfTab} tabTrace
+   * @param {Array<ToplevelEvent>} topLevelEvents
    * @param {number} startTime Optional start time (in ms relative to navstart) of range of interest. Defaults to navstart.
    * @param {number} endTime Optional end time (in ms relative to navstart) of range of interest. Defaults to trace end.
    * @return {{durations: Array<number>, clippedLength: number}}
    */
-  static getMainThreadTopLevelEventDurations(tabTrace, startTime = 0, endTime = Infinity) {
-    const topLevelEvents = TraceProcessor.getMainThreadTopLevelEvents(tabTrace, startTime, endTime);
-
+  static getMainThreadTopLevelEventDurations(topLevelEvents, startTime = 0, endTime = Infinity) {
     // Find durations of all slices in range of interest.
     /** @type {Array<number>} */
     const durations = [];
     let clippedLength = 0;
 
     topLevelEvents.forEach(event => {
+      if (event.end < startTime || event.start > endTime) {
+        return;
+      }
+
       let duration = event.duration;
       let eventStart = event.start;
       if (eventStart < startTime) {
@@ -149,7 +151,7 @@ class TraceProcessor {
    * @param {LH.Artifacts.TraceOfTab} tabTrace
    * @param {number=} startTime Optional start time (in ms relative to navstart) of range of interest. Defaults to navstart.
    * @param {number=} endTime Optional end time (in ms relative to navstart) of range of interest. Defaults to trace end.
-   * @return {!Array<{start: number, end: number, duration: number}>}
+   * @return {Array<ToplevelEvent>}
    */
   static getMainThreadTopLevelEvents(tabTrace, startTime = 0, endTime = Infinity) {
     const topLevelEvents = [];
@@ -186,4 +188,11 @@ class TraceProcessor {
   }
 }
 
+/**
+ * @typedef ToplevelEvent
+ * @prop {number} start
+ * @prop {number} end
+ * @prop {number} duration
+ */
+
 module.exports = TraceProcessor;

lighthouse-core/test/audits/estimated-input-latency-test.js

@@ -5,12 +5,13 @@
  */
 'use strict';
 
-const Audit = require('../../audits/estimated-input-latency.js');
-const Runner = require('../../runner.js');
+const Audit = require('../../audits/estimated-input-latency');
+const Runner = require('../../runner');
 const assert = require('assert');
 const options = Audit.defaultOptions;
 
-const pwaTrace = require('../fixtures/traces/progressive-app.json');
+const TracingProcessor = require('../../lib/traces/tracing-processor');
+const pwaTrace = require('../fixtures/traces/progressive-app-m60.json');
 
 const computedArtifacts = Runner.instantiateComputedArtifacts();
 
@@ -25,12 +26,63 @@ function generateArtifactsWithTrace(trace) {
 
 describe('Performance: estimated-input-latency audit', () => {
   it('evaluates valid input correctly', () => {
-    const artifacts = generateArtifactsWithTrace({traceEvents: pwaTrace});
+    const artifacts = generateArtifactsWithTrace(pwaTrace);
     return Audit.audit(artifacts, {options}).then(output => {
       assert.equal(output.debugString, undefined);
-      assert.equal(output.rawValue, 16.2);
-      assert.equal(output.displayValue, '16\xa0ms');
+      assert.equal(Math.round(output.rawValue * 10) / 10, 17.1);
+      assert.equal(output.displayValue, '17\xa0ms');
       assert.equal(output.score, 1);
     });
   });
+
+  describe('#audit', () => {
+    let firstMeaningfulPaint;
+    let traceEnd;
+    let artifacts;
+    let origGetMainThreadEventsFn;
+    let mainThreadEvtsMock;
+
+    beforeEach(() => {
+      firstMeaningfulPaint = 0.00001;
+      traceEnd = 1e20;
+      artifacts = {
+        traces: {},
+        requestTraceOfTab() {
+          const timings = {firstMeaningfulPaint, traceEnd};
+          return Promise.resolve({timings});
+        },
+      };
+
+      origGetMainThreadEventsFn = TracingProcessor.getMainThreadTopLevelEvents;
+      TracingProcessor.getMainThreadTopLevelEvents = () => mainThreadEvtsMock(arguments);
+    });
+
+    afterEach(() => {
+      TracingProcessor.getMainThreadTopLevelEvents = origGetMainThreadEventsFn;
+    });
+
+    it('uses a 5s rolling window, not traceEnd', async () => {
+      mainThreadEvtsMock = () => [
+        {start: 7500, end: 10000, duration: 2500},
+        {start: 10000, end: 15000, duration: 5000},
+      ];
+
+      const result = await Audit.audit(artifacts, {options});
+      assert.equal(result.rawValue, 4516);
+      assert.equal(result.score, 0);
+    });
+
+    it('handles continuous tasks', async () => {
+      const events = [];
+      for (let i = 0; i < 1000; i++) {
+        events.push({start: i * 100, end: (i + 1) * 100, duration: 100});
+      }
+
+      mainThreadEvtsMock = () => events;
+
+      const result = await Audit.audit(artifacts, {options});
+      assert.equal(result.rawValue, 106);
+      assert.equal(result.score, 0.44);
+    });
+  });
 });

lighthouse-core/test/lib/traces/tracing-processor-test.js

@@ -191,7 +191,8 @@ describe('TracingProcessor lib', () => {
     it('gets durations of top-level tasks', () => {
       const trace = {traceEvents: pwaTrace};
       const tabTrace = new TraceOfTab().compute_(trace);
-      const ret = TracingProcessor.getMainThreadTopLevelEventDurations(tabTrace);
+      const events = TracingProcessor.getMainThreadTopLevelEvents(tabTrace);
+      const ret = TracingProcessor.getMainThreadTopLevelEventDurations(events);
       const durations = ret.durations;
 
       function getDurationFromIndex(index) {
@@ -225,7 +226,8 @@ describe('TracingProcessor lib', () => {
     it('compute correct defaults', () => {
       const trace = {traceEvents: pwaTrace};
       const tabTrace = new TraceOfTab().compute_(trace);
-      const ret = TracingProcessor.getRiskToResponsiveness(tabTrace);
+      const events = TracingProcessor.getMainThreadTopLevelEvents(tabTrace);
+      const ret = TracingProcessor.getRiskToResponsiveness(events, 0, tabTrace.timings.traceEnd);
       assert.equal(ret.durations.length, 645);
       assert.equal(Math.round(ret.totalTime), 2143);
       assert.equal(ret.clippedLength, 0);

lighthouse-core/test/results/sample_v2.json

@@ -224,34 +224,10 @@
       "score": 1,
       "displayValue": "16 ms",
       "rawValue": 16,
-      "extendedInfo": {
-        "value": [
-          {
-            "percentile": 0.5,
-            "time": 16
-          },
-          {
-            "percentile": 0.75,
-            "time": 16
-          },
-          {
-            "percentile": 0.9,
-            "time": 16
-          },
-          {
-            "percentile": 0.99,
-            "time": 92.83829500000138
-          },
-          {
-            "percentile": 1,
-            "time": 138.53700000000208
-          }
-        ]
-      },
       "scoreDisplayMode": "numeric",
       "name": "estimated-input-latency",
       "description": "Estimated Input Latency",
-      "helpText": "The score above is an estimate of how long your app takes to respond to user input, in milliseconds. There is a 90% probability that a user encounters this amount of latency, or less. 10% of the time a user can expect additional latency. If your latency is higher than 50 ms, users may perceive your app as laggy. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/estimated-input-latency)."
+      "helpText": "The score above is an estimate of how long your app takes to respond to user input, in milliseconds, during the busiest 5s window of page load. If your latency is higher than 50 ms, users may perceive your app as laggy. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/estimated-input-latency)."
     },
     "errors-in-console": {
       "score": 0,
@@ -5385,6 +5361,6 @@
     }
   },
   "timing": {
-    "total": 836
+    "total": 931
   }
 }