Facebook/react-native
1
0
Fork 0
mirror of https://github.com/facebook/react-native.git synced 2025-11-01 09:14:26 +00:00
Code Issues Packages Projects Releases Wiki Activity
Files
gh-pages
react-native/docs/profile-hermes.html
T
Website Deployment Script a47f46805e Deploy website - based on 8110ed5b69a61331dbe9ba0e08241c84950cf52f
2021-03-13 08:44:52 +00:00

52 lines
48 KiB
HTML
Raw Permalink Blame History

<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1">
<meta name="generator" content="Docusaurus v2.0.0-alpha.70">
<link rel="alternate" type="application/rss+xml" href="/blog/rss.xml" title="React Native Blog RSS Feed">
<link rel="alternate" type="application/atom+xml" href="/blog/atom.xml" title="React Native Blog Atom Feed">
<link rel="preconnect" href="https://www.google-analytics.com">
<script>window.ga=window.ga||function(){(ga.q=ga.q||[]).push(arguments)},ga.l=+new Date,ga("create","UA-41298772-2","auto"),ga("send","pageview")</script>
<script async src="https://www.google-analytics.com/analytics.js"></script>
<link rel="preconnect" href="https://www.google-analytics.com">
<link rel="preconnect" href="https://www.googletagmanager.com">
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-41298772-2"></script>
<script>function gtag(){dataLayer.push(arguments)}window.dataLayer=window.dataLayer||[],gtag("js",new Date),gtag("config","UA-41298772-2",{})</script>
<link rel="search" type="application/opensearchdescription+xml" title="React Native" href="/opensearch.xml">
<link rel="icon" href="/img/pwa/manifest-icon-512.png">
<link rel="manifest" href="/manifest.json">
<meta name="theme-color" content="#20232a">
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-status-bar-style" content="#20232a">
<link rel="apple-touch-icon" href="/img/pwa/manifest-icon-512.png">
<link rel="mask-icon" href="/img/pwa/manifest-icon-512.png" color="#06bcee">
<meta name="msapplication-TileImage" href="/img/pwa/manifest-icon-512.png">
<meta name="msapplication-TileColor" content="#20232a">
<script src="https://cdn.jsdelivr.net/npm/focus-visible@5.2.0/dist/focus-visible.min.js" defer="defer"></script>
<script src="https://snack.expo.io/embed.js" defer="defer"></script><title data-react-helmet="true">Profiling with Hermes · React Native</title><meta data-react-helmet="true" name="twitter:image:alt" content="Image for React Native"><meta data-react-helmet="true" name="docsearch:language" content="en"><meta data-react-helmet="true" name="docsearch:version" content="0.64"><meta data-react-helmet="true" name="docsearch:docusaurus_tag" content="docs-default-0.64"><meta data-react-helmet="true" property="og:image" content="https://reactnative.dev/img/logo-og.png"><meta data-react-helmet="true" name="twitter:card" content="summary"><meta data-react-helmet="true" name="twitter:image" content="https://reactnative.dev/img/logo-og.png"><meta data-react-helmet="true" property="og:title" content="Profiling with Hermes · React Native"><meta data-react-helmet="true" name="description" content="You can visualize JavaScript&#x27;s performance in a React Native app using Hermes. Hermes is a small and lightweight JavaScript engine optimized for running React Native on Android (you can read more about using it with React Native here. Hermes helps improve app performance and also exposes ways to analyze the performance of the JavaScript that it runs."><meta data-react-helmet="true" property="og:description" content="You can visualize JavaScript&#x27;s performance in a React Native app using Hermes. Hermes is a small and lightweight JavaScript engine optimized for running React Native on Android (you can read more about using it with React Native here. Hermes helps improve app performance and also exposes ways to analyze the performance of the JavaScript that it runs."><meta data-react-helmet="true" property="og:url" content="https://reactnative.dev/docs/profile-hermes"><link data-react-helmet="true" rel="shortcut icon" href="/img/favicon.ico"><link data-react-helmet="true" rel="preconnect" href="https://BH4D9OD16A-dsn.algolia.net" crossorigin="anonymous"><link data-react-helmet="true" rel="canonical" href="https://reactnative.dev/docs/profile-hermes"><link rel="stylesheet" href="/styles.f56da522.css">
<link rel="stylesheet" href="/main.3de2b5ef.css">
<link rel="preload" href="/styles.9d29dd5a.js" as="script">
<link rel="preload" href="/runtime~main.b00a5634.js" as="script">
<link rel="preload" href="/main.4103a08e.js" as="script">
<link rel="preload" href="/1.7a6193e2.js" as="script">
<link rel="preload" href="/2.9b40dc51.js" as="script">
<link rel="preload" href="/1089.caa7a648.js" as="script">
<link rel="preload" href="/1f03ab5e.a02daabd.js" as="script">
<link rel="preload" href="/17896441.b54b3e3c.js" as="script">
<link rel="preload" href="/573e67af.d395525e.js" as="script">
</head>
<body>
<script>!function(){function t(t){document.documentElement.setAttribute("data-theme",t)}var e=function(){var t=null;try{t=localStorage.getItem("theme")}catch(t){}return t}();t(null!==e?e:"light")}()</script><div id="__docusaurus">
<nav aria-label="Skip navigation links"><button type="button" tabindex="0" class="skipToContent_3aLp">Skip to main content</button></nav><nav class="navbar navbar--fixed-top navbar--dark"><div class="navbar__inner"><div class="navbar__items"><div aria-label="Navigation bar toggle" class="navbar__toggle" role="button" tabindex="0"><svg aria-label="Menu" width="30" height="30" viewBox="0 0 30 30" role="img" focusable="false"><title>Menu</title><path stroke="currentColor" stroke-linecap="round" stroke-miterlimit="10" stroke-width="2" d="M4 7h22M4 15h22M4 23h22"></path></svg></div><a class="navbar__brand" href="/"><img src="/img/header_logo.svg" alt="React Native" class="themedImage_phiS themedImage--light_VJaY navbar__logo"><img src="/img/header_logo.svg" alt="React Native" class="themedImage_phiS themedImage--dark_1NF3 navbar__logo"><strong class="navbar__title">React Native</strong></a><div class="navbar__item dropdown dropdown--hoverable dropdown--left"><a class="navbar__item navbar__link" href="/docs/getting-started">0.64</a><ul class="dropdown__menu"><li><a class="dropdown__link" href="/docs/next/profile-hermes">Next</a></li><li><a aria-current="page" class="dropdown__link dropdown__link--active" href="/docs/profile-hermes">0.64</a></li><li><a class="dropdown__link" href="/docs/0.63/getting-started">0.63</a></li><li><a class="dropdown__link" href="/docs/0.62/getting-started">0.62</a></li><li><a class="dropdown__link" href="/docs/0.61/getting-started">0.61</a></li><li><a class="dropdown__link" href="/docs/0.60/getting-started">0.60</a></li><li><a class="dropdown__link" href="/versions">All versions</a></li></ul></div></div><div class="navbar__items navbar__items--right"><a class="navbar__item navbar__link navbar__link--active" href="/docs/getting-started">Docs</a><a class="navbar__item navbar__link" href="/docs/components-and-apis">Components</a><a class="navbar__item navbar__link" href="/docs/accessibilityinfo">API</a><a class="navbar__item navbar__link" href="/help">Community</a><a class="navbar__item navbar__link" href="/blog">Blog</a><a href="https://github.com/facebook/react-native" target="_blank" rel="noopener noreferrer" class="navbar__item navbar__link navbar-github-link" aria-label="GitHub repository"></a><div class="react-toggle react-toggle--disabled displayOnlyInLargeViewport_Bh6k"><div class="react-toggle-track"><div class="react-toggle-track-check"><span class="toggle_1UDy">🌜</span></div><div class="react-toggle-track-x"><span class="toggle_1UDy">🌞</span></div></div><div class="react-toggle-thumb"></div><input type="checkbox" disabled="" aria-label="Dark mode toggle" class="react-toggle-screenreader-only"></div><button type="button" class="DocSearch DocSearch-Button" aria-label="Search"><span class="DocSearch-Button-Container"><svg width="20" height="20" class="DocSearch-Search-Icon" viewBox="0 0 20 20"><path d="M14.386 14.386l4.0877 4.0877-4.0877-4.0877c-2.9418 2.9419-7.7115 2.9419-10.6533 0-2.9419-2.9418-2.9419-7.7115 0-10.6533 2.9418-2.9419 7.7115-2.9419 10.6533 0 2.9419 2.9418 2.9419 7.7115 0 10.6533z" stroke="currentColor" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg><span class="DocSearch-Button-Placeholder">Search</span></span></button></div></div><div role="presentation" class="navbar-sidebar__backdrop"></div><div class="navbar-sidebar"><div class="navbar-sidebar__brand"><a class="navbar__brand" href="/"><img src="/img/header_logo.svg" alt="React Native" class="themedImage_phiS themedImage--light_VJaY navbar__logo"><img src="/img/header_logo.svg" alt="React Native" class="themedImage_phiS themedImage--dark_1NF3 navbar__logo"><strong class="navbar__title">React Native</strong></a></div><div class="navbar-sidebar__items"><div class="menu"><ul class="menu__list"><li class="menu__list-item"><a class="menu__link navbar__link--active" href="/docs/getting-started">Docs</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/components-and-apis">Components</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/accessibilityinfo">API</a></li><li class="menu__list-item"><a class="menu__link" href="/help">Community</a></li><li class="menu__list-item"><a class="menu__link" href="/blog">Blog</a></li><li class="menu__list-item"><a role="button" class="menu__link menu__link--sublist">Versions</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" href="/docs/next/profile-hermes">Next</a></li><li class="menu__list-item"><a aria-current="page" class="menu__link menu__link--active" href="/docs/profile-hermes">0.64</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/0.63/getting-started">0.63</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/0.62/getting-started">0.62</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/0.61/getting-started">0.61</a></li><li class="menu__list-item"><a class="menu__link" href="/docs/0.60/getting-started">0.60</a></li><li class="menu__list-item"><a class="menu__link" href="/versions">All versions</a></li></ul></li><li class="menu__list-item"><a href="https://github.com/facebook/react-native" target="_blank" rel="noopener noreferrer" class="menu__link navbar-github-link" aria-label="GitHub repository"></a></li></ul></div></div></div></nav><div class="main-wrapper"><div class="docPage_1mVJ"><div class="docSidebarContainer_uPTz" role="complementary"><div class="sidebar_M-Lc"><div class="menu menu--responsive thin-scrollbar menu_tgpy"><button aria-label="Open Menu" aria-haspopup="true" class="button button--secondary button--sm menu__button" type="button"><svg aria-label="Menu" class="sidebarMenuIcon_1e05" width="24" height="24" viewBox="0 0 30 30" role="img" focusable="false"><title>Menu</title><path stroke="currentColor" stroke-linecap="round" stroke-miterlimit="10" stroke-width="2" d="M4 7h22M4 15h22M4 23h22"></path></svg></button><ul class="menu__list"><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">The Basics</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/getting-started">Introduction</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/intro-react-native-components">Core Components and Native Components</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/intro-react">React Fundamentals</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/handling-text-input">Handling Text Input</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/using-a-scrollview">Using a ScrollView</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/using-a-listview">Using List Views</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/troubleshooting">Troubleshooting</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/platform-specific-code">Platform Specific Code</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/more-resources">More Resources</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Environment setup</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/environment-setup">Setting up the development environment</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/integration-with-existing-apps">Integration with Existing Apps</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/integration-with-android-fragment">Integration with an Android Fragment</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/building-for-tv">Building For TV Devices</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/out-of-tree-platforms">Out-of-Tree Platforms</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Workflow</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/running-on-device">Running On Device</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/fast-refresh">Fast Refresh</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/debugging">Debugging</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/symbolication">Symbolicating a stack trace</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/testing-overview">Testing</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/libraries">Using Libraries</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/typescript">Using TypeScript</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/upgrading">Upgrading to new versions</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Design</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/style">Style</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/height-and-width">Height and Width</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/flexbox">Layout with Flexbox</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/images">Images</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/colors">Color Reference</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Interaction</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/handling-touches">Handling Touches</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/navigation">Navigating Between Screens</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/animations">Animations</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/gesture-responder-system">Gesture Responder System</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Inclusion</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/accessibility">Accessibility</a></li></ul></li><li class="menu__list-item"><a class="menu__link menu__link--sublist menu__link--active" href="#!">Performance</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/performance">Performance Overview</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/optimizing-flatlist-configuration">Optimizing Flatlist Configuration</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/ram-bundles-inline-requires">RAM Bundles and Inline Requires</a></li><li class="menu__list-item"><a class="menu__link" tabindex="0" href="/docs/profiling">Profiling</a></li><li class="menu__list-item"><a aria-current="page" class="menu__link menu__link--active active" tabindex="0" href="/docs/profile-hermes">Profiling with Hermes</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">JavaScript Runtime</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/javascript-environment">JavaScript Environment</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/timers">Timers</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/hermes">Using Hermes</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Connectivity</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/network">Networking</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/security">Security</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Native Modules</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-modules-intro">Native Modules Intro</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-modules-android">Android Native Modules</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-modules-ios">iOS Native Modules</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-modules-setup">Native Modules NPM Package Setup</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Native Components</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-components-android">Android Native UI Components</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/native-components-ios">iOS Native UI Components</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/direct-manipulation">Direct Manipulation</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Guides (Android)</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/headless-js-android">Headless JS</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/signed-apk-android">Publishing to Google Play Store</a></li></ul></li><li class="menu__list-item menu__list-item--collapsed"><a class="menu__link menu__link--sublist" href="#!">Guides (iOS)</a><ul class="menu__list"><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/linking-libraries-ios">Linking Libraries</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/running-on-simulator-ios">Running On Simulator</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/communication-ios">Communication between native and React Native</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/app-extensions">App Extensions</a></li><li class="menu__list-item"><a class="menu__link" tabindex="-1" href="/docs/publishing-to-app-store">Publishing to Apple App Store</a></li></ul></li></ul></div></div></div><main class="docMainContainer_1zi2"><div class="container padding-vert--lg docItemWrapper_1hMI"><div class="row"><div class="col docItemCol_2AGf"><div class="docItemContainer_1tAC"><article><header><h1 class="docTitle_cWlf">Profiling with Hermes</h1></header><div class="markdown"><p>You can visualize JavaScript&#x27;s performance in a React Native app using <a href="https://github.com/facebook/hermes" target="_blank" rel="noopener noreferrer">Hermes</a>. Hermes is a small and lightweight JavaScript engine optimized for running React Native on Android (you can <a href="/docs/hermes">read more about using it with React Native here</a>. Hermes helps improve app performance and also exposes ways to analyze the performance of the JavaScript that it runs.</p><p>In this section, you will learn how to profile your React Native app running on Hermes and how to visualize the profile using <a href="https://developers.google.com/web/tools/chrome-devtools/evaluate-performance/reference" target="_blank" rel="noopener noreferrer">the Performance tab on Chrome DevTools</a></p><blockquote><p>Be sure to <a href="/docs/hermes">enable hermes in your app</a> before you get started!</p></blockquote><p>Follow the instructions below to get started profiling:</p><ol><li><a href="/docs/profile-hermes#record-a-hermes-sampling-profile">Record a Hermes sampling profile</a></li><li><a href="/docs/profile-hermes#execute-command-from-cli">Execute command from CLI</a></li><li><a href="/docs/profile-hermes#open-the-downloaded-profile-on-chrome-devtools">Open the downloaded profile on Chrome DevTools</a></li></ol><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="record-a-hermes-sampling-profile"></a>Record a Hermes sampling profile<a class="hash-link" href="#record-a-hermes-sampling-profile" title="Direct link to heading">#</a></h2><p>To record a sampling profiler from the Developer Menu:</p><ol><li>Navigate to your running Metro server terminal.</li><li>Press <code>d</code> to open the <strong>Developer Menu.</strong></li><li>Select <strong>Enable Sampling Profiler.</strong></li><li>Execute your JavaScript by in your app (press buttons, etc.)</li><li>Open the <strong>Developer Menu</strong> by pressing <code>d</code> again.</li><li>Select <strong>Disable Sampling Profiler</strong> to stop recording and save the sampling profiler.</li></ol><p>A toast will show the location where the sampling profiler has been saved, usually in <code>/data/user/0/com.appName/cache/*.cpuprofile</code></p><img src="/docs/assets/HermesProfileSaved.png" height="465" width="250" alt="Toast Notification of Profile saving"><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="execute-command-from-cli"></a>Execute command from CLI<a class="hash-link" href="#execute-command-from-cli" title="Direct link to heading">#</a></h2><p>You can use the <a href="https://github.com/react-native-community/cli" target="_blank" rel="noopener noreferrer">React Native CLI</a> to convert the Hermes tracing profile to Chrome tracing profile, and then pull it to your local machine using:</p><div class="mdxCodeBlock_1daz"><div class="codeBlockContent_2es_"><div tabindex="0" class="prism-code language-sh codeBlock_27aQ thin-scrollbar"><div class="codeBlockLines_2rCb" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain">npx react-native profile-hermes [destinationDir]</span></div></div></div><button type="button" aria-label="Copy code to clipboard" class="copyButton_2bml">Copy</button></div></div><h3><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="enabling-source-map"></a>Enabling source map<a class="hash-link" href="#enabling-source-map" title="Direct link to heading">#</a></h3><p>A source map is used to enhance the profile and associate trace events with the application code. You can automatically generate a source map when converting the Hermes tracing profile to a Chrome tracing profile by enabling <code>bundleInDebug</code> if the app is running in development mode. This allows React Native to build the bundle during its running process. Here&#x27;s how:</p><ol><li>In your app&#x27;s <code>android/app/build.gradle</code> file, add:</li></ol><div class="mdxCodeBlock_1daz"><div class="codeBlockContent_2es_"><div tabindex="0" class="prism-code language-java codeBlock_27aQ thin-scrollbar"><div class="codeBlockLines_2rCb" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain">project.ext.react = [</span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> bundleInDebug: true,</span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain">]</span></div></div></div><button type="button" aria-label="Copy code to clipboard" class="copyButton_2bml">Copy</button></div></div><blockquote><p>Be sure to clean the build whenever you make any changes to <code>build.gradle</code></p></blockquote><ol start="2"><li>Clean the build by running:</li></ol><div class="mdxCodeBlock_1daz"><div class="codeBlockContent_2es_"><div tabindex="0" class="prism-code language-sh codeBlock_27aQ thin-scrollbar"><div class="codeBlockLines_2rCb" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain">cd android &amp;&amp; ./gradlew clean</span></div></div></div><button type="button" aria-label="Copy code to clipboard" class="copyButton_2bml">Copy</button></div></div><ol start="3"><li>Run your app:</li></ol><div class="mdxCodeBlock_1daz"><div class="codeBlockContent_2es_"><div tabindex="0" class="prism-code language-sh codeBlock_27aQ thin-scrollbar"><div class="codeBlockLines_2rCb" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain">npx react-native run-android</span></div></div></div><button type="button" aria-label="Copy code to clipboard" class="copyButton_2bml">Copy</button></div></div><h3><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="common-errors"></a>Common errors<a class="hash-link" href="#common-errors" title="Direct link to heading">#</a></h3><h4><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="adb-no-devicesemulators-found-or-adb-device-offline"></a><code>adb: no devices/emulators found</code> or <code>adb: device offline</code><a class="hash-link" href="#adb-no-devicesemulators-found-or-adb-device-offline" title="Direct link to heading">#</a></h4><ul><li><strong>Why this happens</strong> The CLI cannot access the device or emulator (through adb) you are using to run the app.</li><li><strong>How to fix</strong> Make sure your Android device/emulator is connected and running. The command only works when it can access adb.</li></ul><h4><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="there-is-no-file-in-the-cache-directory"></a><code>There is no file in the cache/ directory</code><a class="hash-link" href="#there-is-no-file-in-the-cache-directory" title="Direct link to heading">#</a></h4><ul><li><strong>Why this happens</strong> The CLI cannot find any <strong>.cpuprofile</strong> file in your app&#x27;s <strong>cache/</strong> directory. You might have forgotten to record a profile from the device.</li><li><strong>How to fix</strong> Follow the <a href="/docs/profile-hermes#record-a-hermes-sampling-profile">instructions</a> to enable/disable profiler from device.</li></ul><h4><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="error-your_profile_namecpuprofile-is-an-empty-file"></a><code>Error: your_profile_name.cpuprofile is an empty file</code><a class="hash-link" href="#error-your_profile_namecpuprofile-is-an-empty-file" title="Direct link to heading">#</a></h4><ul><li><strong>Why this happens</strong> The profile is empty, it might be because Hermes is not running correctly.</li><li><strong>How to fix</strong> Make sure your app is running on the latest version of Hermes.</li></ul><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="open-the-downloaded-profile-in-chrome-devtools"></a>Open the downloaded profile in Chrome DevTools<a class="hash-link" href="#open-the-downloaded-profile-in-chrome-devtools" title="Direct link to heading">#</a></h2><p>To open the profile in Chrome DevTools:</p><ol><li><p>Open Chrome DevTools.</p></li><li><p>Select the <strong>Performance</strong> tab.</p></li><li><p>Right click and choose <strong>Load profile...</strong></p><img src="/docs/assets/openChromeProfile.png" alt="Loading a performance profile on Chrome DevTools"></li></ol><h2><a aria-hidden="true" tabindex="-1" class="anchor enhancedAnchor_E4oP" id="how-does-the-hermes-profile-transformer-work"></a>How does the Hermes Profile Transformer work?<a class="hash-link" href="#how-does-the-hermes-profile-transformer-work" title="Direct link to heading">#</a></h2><p>The Hermes Sample Profile is of the <code>JSON object format</code>, while the format that Google&#x27;s DevTools supports is <code>JSON Array Format</code>. (More information about the formats can be found on the <a href="https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview" target="_blank" rel="noopener noreferrer">Trace Event Format Document</a>)</p><div class="mdxCodeBlock_1daz"><div class="codeBlockContent_2es_"><div tabindex="0" class="prism-code language-ts codeBlock_27aQ thin-scrollbar"><div class="codeBlockLines_2rCb" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token keyword" style="color:#c5a5c5">export</span><span class="token plain"> </span><span class="token keyword" style="color:#c5a5c5">interface</span><span class="token plain"> </span><span class="token class-name maybe-class-name" style="color:#fac863">HermesCPUProfile</span><span class="token plain"> </span><span class="token punctuation" style="color:#657b83">{</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> traceEvents</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token maybe-class-name">SharedEventProperties</span><span class="token punctuation" style="color:#657b83">[</span><span class="token punctuation" style="color:#657b83">]</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> samples</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token maybe-class-name">HermesSample</span><span class="token punctuation" style="color:#657b83">[</span><span class="token punctuation" style="color:#657b83">]</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> stackFrames</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token punctuation" style="color:#657b83">{</span><span class="token plain"> </span><span class="token punctuation" style="color:#657b83">[</span><span class="token plain">key </span><span class="token keyword" style="color:#c5a5c5">in</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">]</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token maybe-class-name">HermesStackFrame</span><span class="token plain"> </span><span class="token punctuation" style="color:#657b83">}</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"></span><span class="token punctuation" style="color:#657b83">}</span></div></div></div><button type="button" aria-label="Copy code to clipboard" class="copyButton_2bml">Copy</button></div></div><p>The Hermes profile has most of its information encoded into the <code>samples</code> and <code>stackFrames</code> properties. Each sample is a snapshot of the function call stack at that particular timestamp as each sample has a <code>sf</code> property which corresponds to a function call.</p><div class="mdxCodeBlock_1daz"><div class="codeBlockContent_2es_"><div tabindex="0" class="prism-code language-ts codeBlock_27aQ thin-scrollbar"><div class="codeBlockLines_2rCb" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token keyword" style="color:#c5a5c5">export</span><span class="token plain"> </span><span class="token keyword" style="color:#c5a5c5">interface</span><span class="token plain"> </span><span class="token class-name maybe-class-name" style="color:#fac863">HermesSample</span><span class="token plain"> </span><span class="token punctuation" style="color:#657b83">{</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> cpu</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> name</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> ts</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> pid</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">number</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> tid</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> weight</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> </span><span class="token comment" style="color:#93a1a1">/**</span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token comment" style="color:#93a1a1"> * Will refer to an element in the stackFrames object of the Hermes Profile</span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token comment" style="color:#93a1a1"> */</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> sf</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">number</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> stackFrameData</span><span class="token operator" style="color:#fc929e">?</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token maybe-class-name">HermesStackFrame</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"></span><span class="token punctuation" style="color:#657b83">}</span></div></div></div><button type="button" aria-label="Copy code to clipboard" class="copyButton_2bml">Copy</button></div></div><p>The information about a function call can be found in <code>stackFrames</code> which contains key-object pairs, where the key is the <code>sf</code> number and the corresponding object gives us all the relevant information about the function including the <code>sf</code> number of its parent function. This parent-child relationship can be traced upwards to find the information of all the functions running at a particular timestamp.</p><div class="mdxCodeBlock_1daz"><div class="codeBlockContent_2es_"><div tabindex="0" class="prism-code language-ts codeBlock_27aQ thin-scrollbar"><div class="codeBlockLines_2rCb" style="color:#FFFFFF;background:#282C34"><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token keyword" style="color:#c5a5c5">export</span><span class="token plain"> </span><span class="token keyword" style="color:#c5a5c5">interface</span><span class="token plain"> </span><span class="token class-name maybe-class-name" style="color:#fac863">HermesStackFrame</span><span class="token plain"> </span><span class="token punctuation" style="color:#657b83">{</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> line</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> column</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> funcLine</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> funcColumn</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> name</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> category</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">string</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> </span><span class="token comment" style="color:#93a1a1">/**</span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token comment" style="color:#93a1a1"> * A parent function may or may not exist</span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token comment" style="color:#93a1a1"> */</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"> parent</span><span class="token operator" style="color:#fc929e">?</span><span class="token operator" style="color:#fc929e">:</span><span class="token plain"> </span><span class="token builtin" style="color:#2aa198">number</span><span class="token punctuation" style="color:#657b83">;</span><span class="token plain"></span></div><div class="token-line" style="color:#FFFFFF;background:#282C34"><span class="token plain"></span><span class="token punctuation" style="color:#657b83">}</span></div></div></div><button type="button" aria-label="Copy code to clipboard" class="copyButton_2bml">Copy</button></div></div><p>At this point, you should define a few more terms, namely:</p><ol><li>Nodes: The objects corresponding to <code>sf</code> numbers in <code>stackFrames</code></li><li>Active Nodes: The nodes which are currently running at a particular timestamp. A node is classified as running if its <code>sf</code> number is in the function call stack. This call stack can be obtained from the <code>sf</code> number of the sample and tracing upwards till parent <code>sf</code>s are available</li></ol><p>The <code>samples</code> and the <code>stackFrames</code> in tandem can then be used to generate all the start and end events at the corresponding timestamps, wherein:</p><ol><li>Start Nodes/Events: Nodes absent in the previous sample&#x27;s function call stack but present in the current sample&#x27;s.</li><li>End Nodes/Events: Nodes present in the previous sample&#x27;s function call stack but absent in the current sample&#x27;s.</li></ol><img src="/docs/assets/CallStackDemo.jpg" height="800" width="600" alt="CallStack Terms Explained"><p>You can now construct a <code>flamechart</code> of function calls as you have all the function information including its start and end timestamps.</p><p>The <code>hermes-profile-transformer</code> can convert any profile generated using Hermes into a format that can be directly displayed in Chrome DevTools. More information about this can be found on <a href="https://github.com/react-native-community/hermes-profile-transformer" target="_blank" rel="noopener noreferrer"> <code>@react-native-community/hermes-profile-transformer</code> </a></p></div></article><div class="docMetadata margin-vert--xl"><div class="row"><div class="col"><a href="https://github.com/facebook/react-native-website/blob/master/website/versioned_docs/version-0.64/profile-hermes.md" target="_blank" rel="noreferrer noopener"><svg fill="currentColor" height="1.2em" width="1.2em" preserveAspectRatio="xMidYMid meet" role="img" viewBox="0 0 40 40" class="iconEdit_2Hwv"><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"></path></g></svg>Edit this page</a></div><div class="col text--right"><em><small class="docMetadata-updated">Last updated on <time datetime="2021-03-12T19:14:20.000Z" class="docLastUpdatedAt_1gIo">3/12/2021</time></small></em></div></div></div><div class="margin-vert--lg"><nav class="pagination-nav" aria-label="Blog list page navigation"><div class="pagination-nav__item"><a class="pagination-nav__link" href="/docs/profiling"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">« Profiling</div></a></div><div class="pagination-nav__item pagination-nav__item--next"><a class="pagination-nav__link" href="/docs/javascript-environment"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">JavaScript Environment »</div></a></div></nav></div></div></div><div class="col col--3"><div class="tableOfContents_1zTD thin-scrollbar"><ul class="table-of-contents table-of-contents__left-border"><li><a href="#record-a-hermes-sampling-profile" class="table-of-contents__link">Record a Hermes sampling profile</a></li><li><a href="#execute-command-from-cli" class="table-of-contents__link">Execute command from CLI</a><ul><li><a href="#enabling-source-map" class="table-of-contents__link">Enabling source map</a></li><li><a href="#common-errors" class="table-of-contents__link">Common errors</a></li></ul></li><li><a href="#open-the-downloaded-profile-in-chrome-devtools" class="table-of-contents__link">Open the downloaded profile in Chrome DevTools</a></li><li><a href="#how-does-the-hermes-profile-transformer-work" class="table-of-contents__link">How does the Hermes Profile Transformer work?</a></li></ul></div></div></div></div></main></div></div><footer class="footer footer--dark"><div class="container"><div class="row footer__links"><div class="col footer__col"><h4 class="footer__title">Docs</h4><ul class="footer__items"><li class="footer__item"><a class="footer__link-item" href="/docs/getting-started">Getting Started</a></li><li class="footer__item"><a class="footer__link-item" href="/docs/tutorial">Tutorial</a></li><li class="footer__item"><a class="footer__link-item" href="/docs/components-and-apis">Components and APIs</a></li><li class="footer__item"><a class="footer__link-item" href="/docs/more-resources">More Resources</a></li></ul></div><div class="col footer__col"><h4 class="footer__title">Community</h4><ul class="footer__items"><li class="footer__item"><a class="footer__link-item" href="/help">The React Native Community</a></li><li class="footer__item"><a class="footer__link-item" href="/showcase">Who&#x27;s using React Native?</a></li><li class="footer__item"><a href="https://stackoverflow.com/questions/tagged/react-native" target="_blank" rel="noopener noreferrer" class="footer__link-item">Ask Questions on Stack Overflow</a></li><li class="footer__item"><a href="https://github.com/facebook/react-native/blob/master/CONTRIBUTING.md" target="_blank" rel="noopener noreferrer" class="footer__link-item">Contributor Guide</a></li><li class="footer__item"><a href="https://dev.to/t/reactnative" target="_blank" rel="noopener noreferrer" class="footer__link-item">DEV Community</a></li></ul></div><div class="col footer__col"><h4 class="footer__title">Find us</h4><ul class="footer__items"><li class="footer__item"><a class="footer__link-item" href="/blog">Blog</a></li><li class="footer__item"><a href="https://twitter.com/reactnative" target="_blank" rel="noopener noreferrer" class="footer__link-item">Twitter</a></li><li class="footer__item"><a href="https://github.com/facebook/react-native" target="_blank" rel="noopener noreferrer" class="footer__link-item">GitHub</a></li></ul></div><div class="col footer__col"><h4 class="footer__title">More</h4><ul class="footer__items"><li class="footer__item"><a href="https://reactjs.org/" target="_blank" rel="noopener noreferrer" class="footer__link-item">React</a></li><li class="footer__item"><a href="https://opensource.facebook.com/legal/privacy" target="_blank" rel="noopener noreferrer" class="footer__link-item">Privacy Policy</a></li><li class="footer__item"><a href="https://opensource.facebook.com/legal/terms" target="_blank" rel="noopener noreferrer" class="footer__link-item">Terms of Service</a></li></ul></div></div><div class="footer__bottom text--center"><div class="margin-bottom--sm"><a href="https://opensource.facebook.com" target="_blank" rel="noopener noreferrer" class="footerLogoLink_3cAK"><img class="footer__logo" alt="Facebook Open Source Logo" src="/img/oss_logo.png"></a></div><div class="footer__copyright">Copyright © 2021 Facebook, Inc.</div></div></div></footer></div>
<script src="/styles.9d29dd5a.js"></script>
<script src="/runtime~main.b00a5634.js"></script>
<script src="/main.4103a08e.js"></script>
<script src="/1.7a6193e2.js"></script>
<script src="/2.9b40dc51.js"></script>
<script src="/1089.caa7a648.js"></script>
<script src="/1f03ab5e.a02daabd.js"></script>
<script src="/17896441.b54b3e3c.js"></script>
<script src="/573e67af.d395525e.js"></script>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink