chrome-devtools-frontend/front_end/models/trace/lantern/simulation/Constants.ts

Chrome DevTools UI

// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

const DEVTOOLS_RTT_ADJUSTMENT_FACTOR = 3.75;
const DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR = 0.9;

/* eslint-disable @typescript-eslint/naming-convention */
export interface ThrottlingSettings {
  DEVTOOLS_RTT_ADJUSTMENT_FACTOR: number;
  DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR: number;
  mobileSlow4G: {
    rttMs: number,
    throughputKbps: number,
    requestLatencyMs: number,
    downloadThroughputKbps: number,
    uploadThroughputKbps: number,
    cpuSlowdownMultiplier: number,
  };
  mobileRegular3G: {
    rttMs: number,
    throughputKbps: number,
    requestLatencyMs: number,
    downloadThroughputKbps: number,
    uploadThroughputKbps: number,
    cpuSlowdownMultiplier: number,
  };
  desktopDense4G: {
    rttMs: number,
    throughputKbps: number,
    cpuSlowdownMultiplier: number,
    requestLatencyMs: number,
    downloadThroughputKbps: number,
    uploadThroughputKbps: number,
  };
}

const throttling: ThrottlingSettings = {
  DEVTOOLS_RTT_ADJUSTMENT_FACTOR,
  DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR,
  // These values align with WebPageTest's definition of "Fast 3G"
  // But offer similar characteristics to roughly the 75th percentile of 4G connections.
  mobileSlow4G: {
    rttMs: 150,
    throughputKbps: 1.6 * 1024,
    requestLatencyMs: 150 * DEVTOOLS_RTT_ADJUSTMENT_FACTOR,
    downloadThroughputKbps: 1.6 * 1024 * DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR,
    uploadThroughputKbps: 750 * DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR,
    cpuSlowdownMultiplier: 4,
  },
  // These values partially align with WebPageTest's definition of "Regular 3G".
  // These values are meant to roughly align with Chrome UX report's 3G definition which are based
  // on HTTP RTT of 300-1400ms and downlink throughput of <700kbps.
  mobileRegular3G: {
    rttMs: 300,
    throughputKbps: 700,
    requestLatencyMs: 300 * DEVTOOLS_RTT_ADJUSTMENT_FACTOR,
    downloadThroughputKbps: 700 * DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR,
    uploadThroughputKbps: 700 * DEVTOOLS_THROUGHPUT_ADJUSTMENT_FACTOR,
    cpuSlowdownMultiplier: 4,
  },
  // Using a "broadband" connection type
  // Corresponds to "Dense 4G 25th percentile" in https://docs.google.com/document/d/1Ft1Bnq9-t4jK5egLSOc28IL4TvR-Tt0se_1faTA4KTY/edit#heading=h.bb7nfy2x9e5v
  desktopDense4G: {
    rttMs: 40,
    throughputKbps: 10 * 1024,
    cpuSlowdownMultiplier: 1,
    requestLatencyMs: 0,  // 0 means unset
    downloadThroughputKbps: 0,
    uploadThroughputKbps: 0,
  },
};

const Constants: {throttling: ThrottlingSettings} = {
  throttling,
};

export {Constants};