mirror of
https://github.com/facebook/react-native.git
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Emilis Baliukonis
232517a574
Summary: When experimenting with React Profiler API (https://reactjs.org/docs/profiler.html), I noticed that durations are integers without a debugger, but they are doubles with higher precision when debugger is attached. After digging into React Profiler code, I found out that it's using `performance.now()` to accumulate execution times of individual units of work. Since this method does not exist in React Native, it falls back to Javascript `Date`, leading to imprecise results. This PR introduces `global.nativePerformanceNow` function which returns precise native time, and a very basic `performance` polyfill with `now` function. This will greatly improve React Profiler API results, which is essential for profiling and benchmark tools. Solves https://github.com/facebook/react-native/issues/27274 ## Changelog [General] [Added] - Implement `nativePerformanceNow` and `performance.now()` Pull Request resolved: https://github.com/facebook/react-native/pull/27885 Test Plan: ``` const initialTime = global.performance.now(); setTimeout(() => { const newTime = global.performance.now(); console.warn('duration', newTime - initialTime); }, 1000); ``` ### Android + Hermes  ### Android + JSC  ### iOS  Reviewed By: ejanzer Differential Revision: D19888289 Pulled By: rickhanlonii fbshipit-source-id: ab8152382da9aee9b4b3c76f096e45d40f55da6c
57 lines
1.5 KiB
JavaScript
57 lines
1.5 KiB
JavaScript
/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @format
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* @flow strict-local
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*/
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/* globals window: true */
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/**
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* Sets up global variables typical in most JavaScript environments.
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*
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* 1. Global timers (via `setTimeout` etc).
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* 2. Global console object.
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* 3. Hooks for printing stack traces with source maps.
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*
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* Leaves enough room in the environment for implementing your own:
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*
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* 1. Require system.
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* 2. Bridged modules.
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*
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*/
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'use strict';
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const start = Date.now();
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require('./setUpGlobals');
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require('./setUpPerformance');
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require('./setUpSystrace');
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require('./setUpErrorHandling');
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require('./polyfillPromise');
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require('./setUpRegeneratorRuntime');
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require('./setUpTimers');
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require('./setUpXHR');
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require('./setUpAlert');
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require('./setUpNavigator');
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require('./setUpBatchedBridge');
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require('./setUpSegmentFetcher');
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if (__DEV__) {
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require('./checkNativeVersion');
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require('./setUpDeveloperTools');
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}
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const GlobalPerformanceLogger = require('../Utilities/GlobalPerformanceLogger');
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// We could just call GlobalPerformanceLogger.markPoint at the top of the file,
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// but then we'd be excluding the time it took to require the logger.
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// Instead, we just use Date.now and backdate the timestamp.
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GlobalPerformanceLogger.markPoint(
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'initializeCore_start',
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GlobalPerformanceLogger.currentTimestamp() - (Date.now() - start),
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);
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GlobalPerformanceLogger.markPoint('initializeCore_end');
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